JP7348941B2 - Dip molded article containing a layer derived from a latex composition for dip molding - Google Patents

Description

The present invention relates to a dip-molded article comprising a layer derived from a latex composition for dip-molding.

Natural rubber (NR) gloves have a high stress retention rate, good elongation, softness, and excellent so-called rubber elasticity. Therefore, it is widely used in surgical and general gloves. However, the proteins it contains cause type I allergies, so especially in surgical medicine, they are removed as much as possible before use.

Synthetic rubbers such as isoprene rubber (IR) and chloroprene rubber (CR) are used for surgical gloves, but have similar physical properties to natural rubber, but although they do not cause type I allergies, they are complicated and expensive to manufacture.

On the other hand, carboxylated acrylonitrile butadiene rubber (XNBR), which is a synthetic rubber, is inexpensive and widely used as general gloves, but its physical properties are significantly different from those of natural rubber. While the particles of natural rubber are huge, the particles of XNBR are small and covered with surfactant, and in the end, traces of each particle remaining as if they were layered remain, resulting in a low stress retention rate. is extremely low. Also, even though it maintains its physical properties with acrylonitrile, it is inferior to natural rubber in terms of elongation and softness.

Conventionally, XNBR gloves were made stronger by crosslinking the inside and outside of the particles with sulfur and butadiene together with a vulcanization accelerator, and ionic crosslinking between the particles with carboxylic acid and zinc oxide. There were problems such as a decrease in stress retention due to zinc oxide, difficulty in elongation, and hardness. In addition, there was a demand for gloves that were thinner and stronger, so latex itself was preferred to be linear and less entangled, and it also lost its original elasticity and became a plastic-like rubber. was.

In recent years, in order to eliminate type IV allergies caused by vulcanization accelerators in XNBR gloves, accelerator-free gloves using self-crosslinking or organic crosslinking agents have been proposed as an alternative to sulfur crosslinking. Among these, the epoxy crosslinked glove of Patent Document 1 is known to enhance intraparticle crosslinking of XNBR as an alternative to sulfur crosslinking.

On the other hand, interparticle crosslinking has generally been carried out using zinc oxide in order to provide strength and ensure stable production.

This zinc crosslinking was one of the causes of poor stress retention, elongation, and softness of XNBR.

For this reason, it has not been possible to create XNBR gloves that are similar to the NR gloves required for surgical gloves, have a high stress retention rate, have good elongation, and are soft.

Regarding XNBR gloves, there is a proposal for making surgical gloves in Patent Document 2. This is a special XNBR cross-linked with aluminum, but when it is sterilized with gamma rays, which is essential when manufacturing surgical gloves, it becomes partially hard and difficult to stretch, so there is a problem with its practicality.

Aluminum crosslinking has also been proposed as an alternative to crosslinking with sulfur and zinc oxide. Initially, there were problems with aluminum becoming too hard due to its strong bonding strength and instability in the dip liquid, but improvements have been made in recent years.

Patent Document 3 proposes a crosslinking agent of a dihydroxy organoaluminum metal compound having two hydroxyl groups on one aluminum atom using an aluminum salt as a starting material.

Patent Document 4 proposes blending a chelating agent or a polyol with an aluminate salt.

All of these are attempts to eliminate the instability of the aluminum crosslinking agent described above, but the essential crosslinking function of the aluminum crosslinking agent is not fully understood.

International Publication No. 2019/194056 International Publication No. 2017/146238 JP2010-209163 JP2018-9272

The surgical glove standard ASTM D3577-19 requires 500% MD (stress at 500% elongation) of 7 MPa or less, elongation of 650% or more, and TS (tensile strength) of 17 MPa or more. There are no actual products of XNBR gloves that meet this standard.

In addition, the SR (stress retention rate after 5 minutes at 100% elongation), which refers to the inherent rubber elasticity of rubber, is 35 to 45% for conventional XNBR gloves, compared to 75 to 85% for natural rubber gloves. It was only a matter of degree.

The present invention provides a dip-molded product made from a latex composition for dip molding containing a carboxylic acid-modified nitrile copolymer latex containing a carboxylic acid-modified nitrile copolymer that has good stress retention and is easy to stretch. For example, in XNBR gloves, the objective was to provide a glove that has good stress retention, is easy to stretch, and is soft.

In addition, the goal is to create XNBR gloves that meet the standards for surgical gloves and have an SR of 55% or more as the best form, by improving the latex itself, which affects the viscosity and elasticity factors of gloves, and examining and combining cross-linking agents. We examined the effects.

The present invention
(1) A dip-molded product including a layer derived from a latex composition for dip-molding,
The latex composition for dip molding includes a carboxylic acid-modified nitrile copolymer latex,
The carboxylic acid-modified nitrile copolymer latex includes a carboxylic acid-modified nitrile copolymer,
The dip-molded product has an elongation rate greater than 650%, and satisfies the following formulas 1 and 2.

(In the above formula, k ₁ ' is the value obtained by dividing the equilibrium coefficient k ₁ by the thickness of the test piece, and k ₂ ' and k ₃ ' are the viscosity coefficient ( viscous coefficient) is the value obtained by dividing _k2 and _k3 by the thickness of the specimen.)
A dip-molded product, comprising:

(2) The carboxylic acid-modified nitrile copolymer latex satisfies the following formulas 3 and 4,
The carboxylic acid-modified nitrile copolymer contains 18 to 28% by weight of units derived from ethylenically unsaturated nitrile monomers and conjugated diene monomers based on the dry weight of the carboxylic acid-modified nitrile copolymer. Contains 67.5 to 79.5% by weight of units derived from cartilage and 2.5 to 4.5% by weight of units derived from ethylenically unsaturated acid monomers.

(In the above formula, CV ₀ indicates the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a swelled state, and CV _D indicates the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a deswelled state. (Indicates viscosity.)
The dip-molded product described in (1) above,

(3) The unit derived from an ethylenically unsaturated nitrile monomer is acrylonitrile, the unit derived from a conjugated diene monomer is 1,3-butadiene, and the unit derived from an ethylenically unsaturated acid monomer is The dip-molded product according to (2) above, wherein the unit is (meth)acrylic acid;

(4) The dip-molded product according to any one of (1) to (3) above, wherein the latex composition for dip-molding further contains an epoxy crosslinking agent and an aluminum crosslinking agent, as well as water and a pH adjuster. ,

(5) The amount of the epoxy crosslinking agent added is 0.1 to 1.6 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer, and the amount of the aluminum crosslinking agent added is 0.1 to 1.6 parts by weight. , when both the epoxy crosslinking agent and the aluminum crosslinking agent are added, in an amount of 0.1 to 0.8 parts by weight in terms of aluminum oxide, based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer; The dip according to (4) above, wherein the total amount of the epoxy crosslinking agent and the aluminum crosslinking agent added is 0.2 to 1.6 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer. Molding,

(6) The amount of the epoxy crosslinking agent added is 0.2 to 1.0 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer, and the amount of the aluminum crosslinking agent added is 0.2 to 1.0 parts by weight. , when the amount is 0.2 to 0.7 parts by weight in terms of aluminum oxide, based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer, and both the epoxy crosslinking agent and the aluminum crosslinking agent are added. The dip according to (4) above, wherein the total amount of the epoxy crosslinking agent and the aluminum crosslinking agent added is 0.4 to 1.4 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer. Molding,

(7) The epoxy crosslinking agent has three or more glycidyl groups and an alicyclic, aliphatic or aromatic parent skeleton in one molecule, the average number of epoxy groups exceeds 2.25, and MIBK/water distribution The dip-molded product according to any one of (4) to (6) above, wherein the aluminum crosslinking agent is aluminum hydroxyl acid.

(8) A dip-molded article for surgical use, which is sterilized by irradiating the dip-molded article according to any one of (1) to (7) above with γ-rays;

(9) A latex composition for dip molding containing at least a carboxylic acid-modified nitrile copolymer latex, an epoxy crosslinking agent, and an aluminum crosslinking agent,
The carboxylic acid-modified nitrile copolymer latex includes a carboxylic acid-modified nitrile copolymer,
The carboxylic acid-modified nitrile copolymer contains 67.5 to 79.5% by weight of units derived from a conjugated diene monomer and ethylenically unsaturated based on the total content of the carboxylic acid-modified nitrile copolymer. Contains 18 to 28% by weight of units derived from nitrile monomers and 2.5 to 4.5% by weight of units derived from ethylenically unsaturated acid monomers,
The carboxylic acid-modified nitrile copolymer latex satisfies the following formulas 3 and 4,

(In the above equations 3 and 4, the CV ₀ represents the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a swelled state, and the CV _D represents the capillary viscosity of the carboxylic acid-modified copolymer latex in a deswelled state. (indicates capillary viscosity)
The epoxy crosslinking agent has three or more glycidyl groups and an alicyclic, aliphatic or aromatic parent skeleton in one molecule, has an average number of epoxy groups exceeding 2.25, and has an MIBK/water partition ratio of 50%. The above,
The amount of the epoxy crosslinking agent is 0.1 to 1.6 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer,
The aluminum crosslinking agent is aluminum hydroxylate, and the amount of the aluminum crosslinking agent is 0.1 to 0.8 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer.
The sum of the input amounts of the epoxy crosslinking agent and the aluminum crosslinking agent is 0.2 to 1.6 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer,
A latex composition for dip molding whose pH is adjusted to 9.0 to 10.5 with a pH adjuster,

(10)
(i) A maturation step of preparing and stirring the latex composition for dip molding in (9) above (ii) A dipping step of immersing a mold in the latex composition for dip molding (iii) A mold formed on the mold Gelling process to gel the film (iv) Leaching process to remove impurities from the film formed on the mold (v) Beading process to create windings at the ends (vi) Heating and drying at high temperature and finally Including a curing process to complete crosslinking and turn into a cured film as a molded product.
method for producing dip-molded products;

(11)
The carboxylic acid-modified nitrile copolymer latex described in (2) above,
an epoxy crosslinker;
A latex composition for dip molding containing at least an aluminum crosslinking agent.

The present invention provides a dip-molded product made from a carboxylic acid-modified nitrile copolymer that has good stress retention and is easy to stretch, which could not be made using conventional XNBR. Specifically, the present invention provides a glove that is stretchable, soft, and has high stress retention. In the best embodiment, a glove that meets the standards for surgical gloves is provided. This method uses a flexible and soft XNBR that has an optimal acrylonitrile and carboxylic acid content and is made under specially controlled polymerization conditions using the solution of the present invention, and it is enriched with intraparticle crosslinking instead of sulfur. This was achieved by using an epoxy crosslinking agent and aluminum crosslinking between particles instead of zinc. Furthermore, the glove of the present invention is characterized in that its physical properties do not change even after sterilization treatment with gamma rays, which is necessary for surgical gloves, and it is stable.

FIG. 1 is a time-based load graph based on the Maxwell-Weichert model. FIG. 2 is a schematic diagram of the Maxwell-Weichert model.

Preferred embodiments of the present invention will be described below, but it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes may be made. Note that in this specification, "weight" and "mass" are used in the same meaning, and therefore, hereinafter, they will be collectively described as "weight."

In this specification, unless otherwise specified, "%" means "% by weight" and "parts" means "parts by weight."

Furthermore, unless otherwise specified, "parts by weight" generally refers to parts by weight based on 100 parts by weight of the elastomer.

Furthermore, in this specification, when a numerical value or physical property value is used before and after "-" to express it, it is used to include the values before and after it.

1. Technical Features of the Present Invention Molded articles according to embodiments of the present invention have rubber elasticity similar to natural rubber, which has hitherto been considered impossible in XNBR. In other words, it has outstanding stress retention, softness, and elongation. It also has the tensile strength and fatigue durability that gloves require.

The present invention further proposes a crosslinking model that combines an epoxy crosslinker and an aluminum crosslinker as an alternative to the conventional sulfur-vulcanized zinc crosslinker.

Furthermore, for XNBR, we used a latex with unprecedented properties that makes the most of the above combination of crosslinking agents.

This has made it possible to create a glove that combines high levels of elasticity and softness, which were previously difficult to achieve, in a molded article made from XNBR.
The effects of the latex, epoxy crosslinking agent, aluminum crosslinking agent, and combinations thereof in the present invention will be explained.

(1) Latex The carboxylic acid-modified nitrile copolymer in the carboxylic acid-modified nitrile copolymer latex of the present invention includes units derived from a conjugated diene monomer and units derived from an ethylenically unsaturated nitrile monomer. and units derived from ethylenically unsaturated acid monomers.

The carboxylic acid-modified nitrile copolymer latex in the present invention includes a carboxylic acid-modified nitrile copolymer,
The carboxylic acid-modified nitrile copolymer contains 18 to 28% by weight of units derived from ethylenically unsaturated nitrile monomers and 67% by weight of units derived from conjugated diene monomers, based on the dry weight of the copolymer. 5 to 79.5% by weight and 2.5 to 4.5% by weight of units derived from ethylenically unsaturated acid monomers, and
The carboxylic acid-modified nitrile copolymer latex has the following formulas 3 and 4.

(In the above formula, CV ₀ indicates the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a swelled state, and CV _D indicates the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a deswelled state. (Indicates viscosity.)
A carboxylic acid-modified nitrile copolymer latex comprising:

(i) Conjugated diene monomer According to one embodiment of the present invention, the conjugated diene monomer forming the unit derived from the conjugated diene monomer is 1,3-butadiene, 2,3-dimethyl -1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and isoprene may be one or more selected from the group consisting of. As a specific example, the conjugated diene monomer may be 1,3-butadiene or isoprene.

The content of the unit derived from the conjugated diene monomer may be 67.5% to 79.5% by weight based on the total content of the carboxylic acid-modified nitrile copolymer. Within this range, a molded article formed from a latex composition for dip molding containing the carboxylic acid-modified nitrile copolymer is softer, has better elongation, and has better rubber elasticity as the content of the conjugated diene monomer increases. improves.

(ii) Ethylenically unsaturated nitrile monomer According to one embodiment of the present invention, the ethylenically unsaturated nitrile monomer forming the unit derived from the ethylenically unsaturated nitrile monomer is acrylonitrile, It may be one or more selected from the group consisting of methacrylonitrile, fumaronitrile, α-chloronitrile, and α-cyanoethyl acrylonitrile. As a specific example, the ethylenically unsaturated nitrile monomer may be acrylonitrile or methacrylonitrile, and as a more specific example, it may be acrylonitrile.

The content of the ethylenically unsaturated nitrile monomer may be 18% to 28% by weight based on the total content of the carboxylic acid-modified nitrile copolymer. Within this range, a molded article formed from a latex composition for dip molding containing the carboxylic acid-modified nitrile copolymer is softer, has better elongation, and is more rubbery as the content of the ethylenically unsaturated nitrile monomer is lower. Improves elasticity.

(iii) Ethylenically unsaturated acid monomer According to one embodiment of the present invention, the ethylenically unsaturated acid monomer forming the unit derived from the ethylenically unsaturated acid monomer has a carboxyl group, It may also be an ethylenically unsaturated monomer containing an acidic group such as a sulfonic acid group or an acid anhydride group. As specific examples, the ethylenically unsaturated acid monomers include ethylenically unsaturated acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; maleic anhydride, citraconic anhydride, etc. polycarboxylic acid anhydrides; ethylenically unsaturated sulfonic acid monomers such as styrene sulfonic acid; ethylenically unsaturated polycarboxylic acid partial esters such as monobutyl fumarate, monobutyl maleate and mono-2-hydroxypropyl maleate. (partial ester) monomers may be one or more selected from the group consisting of monomers. As a more specific example, the ethylenically unsaturated acid monomer may be one or more selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid; For example, methacrylic acid may be used.

The content of the unit derived from the ethylenically unsaturated acid monomer may be 2.5% to 4.5% by weight based on the total content of the carboxylic acid-modified nitrile copolymer. A molded article formed from a latex composition for dip molding containing the carboxylic acid-modified nitrile copolymer within this range will be softer as the content of units derived from the ethylenically unsaturated acid monomer is smaller. , good elongation and improved rubber elasticity.

(iv) Ethylenically unsaturated monomer The carboxylic acid-modified nitrile copolymer may optionally further contain an ethylenically unsaturated monomer.

The ethylenically unsaturated monomers include hydroxyalkyl (meth)acrylate monomers having 1 to 4 carbon atoms, vinyl aromatic monomers, fluoroalkyl vinyl ether monomers, ethylenically unsaturated amide monomers, and non-ethylenically unsaturated amide monomers. It can contain one or more selected from the group consisting of conjugated diene monomers and ethylenically unsaturated carboxylic acid ester monomers.

The content of the unit derived from the ethylenically unsaturated monomer may be 0.5% to 5% by weight based on the total content of the carboxylic acid-modified nitrile copolymer. Within this range, it is possible to add some properties such as touch and feel to a molded article formed from a latex composition for dip molding containing the carboxylic acid-modified nitrile copolymer.

The characteristics of the monomer composition of the carboxylic acid-modified nitrile copolymer of the present invention described above are achieved by optimizing the contents of the ethylenically unsaturated nitrile monomer and the ethylenically unsaturated acid monomer. It is characterized by improving the softness and elongation of molded products made from carboxylic acid-modified nitrile copolymer latex.

(v) Manufacturing method of carboxylic acid-modified nitrile copolymer In the present invention, the carboxylic acid-modified nitrile copolymer latex has not only the monomer composition of the copolymer but also the manufacturing method exemplified below. By controlling process factors, it is possible to impart unprecedented latex characteristics.

Specifically, the method for producing the carboxylic acid-modified nitrile copolymer latex involves first adding a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, and an ethylenically unsaturated acid monomer to a polymerization reactor. It includes a polymerization step in which the polymer is added to the polymer and polymerized.

The polymerization step is for forming the main chain of the carboxylic acid-modified nitrile copolymer, and the polymerization is carried out by emulsion polymerization. At this time, each monomer is first charged into the polymerization reactor with the type and content of the monomer mentioned above, and each monomer is charged in portions, all at once, or continuously. can.

As for divided feeding, the ethylenically unsaturated nitrile monomer, the conjugated diene monomer, or the ethylenically unsaturated nitrile monomer and the ethylenically unsaturated acid monomer are initially charged. Then, other monomers may be added in the secondary step.

In addition, each monomer may be added separately in the primary, secondary, and tertiary stages, and in that case, it is possible to equalize the distribution of the monomers due to the difference in reaction rate of each monomer. This has the effect of improving the balance between physical properties of molded articles manufactured using the carboxylic acid-modified nitrile copolymer.

Further, the polymerization step can be carried out by adding the monomers, starting stirring, and then adding an emulsifier, a polymerization initiator, an activator, a chain transfer agent, and the like.

As the emulsifier, one or more selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants can be used, and specific examples include alkylbenzene. Sulfonate salts (anionic surfactants) can be used, and more specifically, sodium dodecylbenzenesulfonate can be used. Further, the emulsifier may be added in an amount of 2 to 4 parts by weight based on 100 parts by weight of the total monomer content added during polymerization. Generally, when the amount of emulsifier is large, the particle size of the carboxylic acid-modified nitrile copolymer particles becomes smaller and stability increases.

As the polymerization initiator, a radical initiator can be used, and one or more types selected from the group consisting of inorganic peroxides, organic peroxides, and nitrogen compounds can be used. As a specific example, the polymerization initiator may be an inorganic peroxide, and more specifically, a persulfate, such as potassium persulfate. The polymerization initiator is added in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the total monomer content added in the polymerization process, and the polymerization rate is controlled within this range. It can be maintained at an appropriate level.

Here, when the organic peroxide or the inorganic peroxide is used as a polymerization initiator, it can be used in combination with a reducing agent. As the reducing agent, a compound containing a metal ion in a reduced state, a sulfonic acid compound, or an amine compound can be used alone or in combination of two or more.

When using an activator in the polymerization step, sodium formaldehyde sulfoxylate or the like can be used.
The amount of the activator added is 0 parts by weight to 1 part by weight based on 100 parts by weight of the total monomer content added in the polymerization process, and within this range, the polymerization rate is maintained at an appropriate level. be able to.

As the chain transfer agent, one or more selected from the group consisting of mercaptans, halogenated hydrocarbons, and sulfur-containing compounds can be used. Specific examples include mercaptans, and more specific examples include mercaptans. Alternatively, t-dodecyl mercaptan may be used.

The amount of the chain transfer agent added is, for example, 0.2 parts by weight to 0.9 parts by weight based on 100 parts by weight of the total monomer content added in the polymerization process. Within this range, there is an effect of further improving the balance between physical properties of molded articles manufactured using the carboxylic acid-modified nitrile copolymer.

As a medium, water can be used, as a specific example deionized water. Additionally, during polymerization, additives such as chelating agents, dispersants, pH regulators, oxygen scavengers, particle size regulators, anti-aging agents, and oxygen scavengers may be added as necessary to ensure ease of polymerization. You may also add

In the polymerization process, additives such as an emulsifier, a polymerization initiator, a chain transfer agent, and a medium may be added to the polymerization reactor together or in portions after the monomers are added. If the monomer is added first and stirred before adding the additive, the composition and amount of the monomer dissolved in the aqueous phase at the initial stage of the polymerization reaction will be affected, and this will affect the polymerization. The molecular weight of the carboxylic acid-modified nitrile copolymer and the carboxyl group distribution within the latex particles will change. Moreover, when the monomer is added in portions, the additives can also be added in portions accordingly. In this case, it is easy to control the distribution of monomers due to the difference in reaction rate for each monomer, and the balance between physical properties of molded products manufactured using carboxylic acid-modified nitrile copolymers is improved. It has the effect of causing

The carboxylic acid-modified nitrile copolymer may be polymerized at a temperature of 5°C to 60°C. As long as the temperature is within the above range, there is no problem with the stability of the latex.

Further, the polymerization of the carboxylic acid-modified nitrile copolymer can be carried out by controlling the change in reaction pressure with respect to the initial reaction pressure depending on the polymerization conversion rate to be within a specific range.

Specifically, the range of reaction pressure at the start of polymerization is 2.0 to 2.8 kgf/cm ² , and the reaction pressure is within the range of 1 to 45% at a polymerization conversion rate of 1 to 45%. It is controlled within a range of 15% or less, and in particular, the reaction pressure when the polymerization conversion rate is 40% is in the range of a pressure increase of 5 to 10% compared to the reaction pressure at the start of polymerization.

When the polymerization conversion rate is between 46% and 75%, the reaction pressure is controlled within the range of 5% to 70% of the pressure increase compared to the polymerization initiation reaction pressure.In particular, the reaction pressure when the polymerization conversion rate is 60% is the same as the polymerization initiation reaction pressure. The pressure increase is in the range of 30% to 65% compared to the reaction pressure at the time.

When the polymerization conversion rate is between 76% and the completion of polymerization, the reaction pressure is controlled within the range of 0 to 5% pressure increase compared to the polymerization initiation reaction pressure, or 0 to 100% pressure decrease compared to the polymerization initiation reaction pressure. In particular, the reaction pressure is adjusted so that 90% of the reaction pressure is within a range of 10% or more of the pressure reduction compared to the reaction pressure at the start of polymerization.

The polymerization conversion rate of the polymerization reaction can be measured by a method commonly known in the art. For example, a certain amount of sample is taken out from the reaction composition at certain time intervals, the solid content is measured, and then the polymerization conversion rate is calculated using Equation 5 below.

(In the above formula 5, parts by weight are based on the total monomer content of 100 parts by weight. In the case of section polymerization conversion rate, it reflects the parts by weight of monomers and parts by weight of additives added up to the relevant section. (It can be calculated as follows.)

If the change in reaction pressure with respect to the initial reaction pressure due to the polymerization conversion rate is adjusted to be within the above range, the composition and amount of monomers dissolved in the aqueous phase will be influenced by the reaction pressure during the progress of the polymerization reaction. These influences affect the degree of entanglement, reluctance to unravel, and branched structure of the carboxylic acid-modified nitrile copolymer.

The method for producing the carboxylic acid-modified nitrile copolymer latex further includes the step of completing the polymerization reaction and obtaining the carboxylic acid-modified nitrile copolymer latex. The polymerization reaction is terminated by cooling the polymerization system when the polymerization conversion rate is 85% or more, or by adding a polymerization terminator, a pH regulator, and an antioxidant.

The method for producing the carboxylic acid-modified nitrile copolymer latex may further include a step of removing unreacted monomers by a deodorizing step after the reaction is completed.

In the present invention, in order to make the physical properties of molded products such as rubber gloves that are cross-linked with a cross-linking agent described later by dip-molding the latex with good elasticity and softness, the monomers in the latex are Regarding the composition, the amounts of ethylenically unsaturated nitrile monomer and ethylenically unsaturated acid monomer were optimized. Furthermore, the structure of the latex particles was optimized by controlling the polymerization process and adjusting the degree of entanglement, resistance to unraveling, branching structure, molecular weight, carboxyl group distribution within the latex particles, etc. of the carboxylic acid-modified nitrile copolymer. This affected the elastic and viscous physical properties of the latex moldings made.

The carboxylic acid-modified nitrile copolymer of the present invention has entanglements that dramatically increase rubber elasticity, so-called stress retention, when crosslinked later with a crosslinking agent, and latex that is difficult to unravel. It is preferable to have a structure. In addition, in order to have softness and elongation and to minimize fluctuations in physical properties even after irradiation with gamma rays, it is preferable that the molecular weight of the copolymer be appropriate and that the carboxyl groups distributed within the latex particles be optimized. Such a carboxylic acid-modified nitrile copolymer can be produced using the copolymer composition and polymerization method described above. In the present invention, the physical properties of the carboxylic acid-modified nitrile copolymer were adjusted using the various parameters shown below, and the numerical range of the parameters that satisfied the physical properties sought by the present inventors was determined.

The carboxylic acid-modified nitrile copolymer latex preferably satisfies the following formulas 3 and 4 at the same time.

In Equation 3, CV ₀ represents the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a swelling state.
In Equation 4, CV ₀ is as described above, and CV _D represents the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a deswelled state.

In this way, by controlling various factors in the composition and polymerization method of the carboxylic acid-modified nitrile copolymer, the capillary viscosity is adjusted to a range of 1.0 to 3.0 mm ² /s, and the P value is adjusted to 0. By adjusting it within the range of 8 to 1, it is possible to optimize the viscosity and elastic properties of a molded article molded from a latex composition for dip molding containing the carboxylic acid-modified nitrile copolymer. As a result, molded articles made from the dip-molding latex composition are flexible, have excellent feel and feel when worn, and have excellent elasticity.

The capillary viscosity CV ₀ in Equation 3 is the capillary viscosity measured when the carboxylic acid-modified nitrile copolymer is swollen. Capillary viscosity is generally used as a means of measuring the molecular weight of non-crosslinked polymers. However, in the present invention, CV ₀ is different from such a general capillary viscosity, and refers to a capillary viscosity measured in a state in which the copolymer particles in the latex are swollen in a methyl ethyl ketone solvent, that is, in a swelling state.

Therefore, such CV ₀ can provide information about the molecular weight of the copolymer in the carboxylic acid-modified nitrile copolymer latex and the factors that affect swelling by methyl ethyl ketone solvent, and among these information In particular, information regarding the carboxyl group distribution of the copolymer within latex particles can be effectively obtained. In other words, a carboxylic acid-modified nitrile copolymer latex that satisfies the CV ₀ range has an appropriate level of copolymer molecular weight and carboxyl group distribution in the copolymer within the latex particles, and is processed by dip molding. When used as a latex composition, it may affect the optimization of the viscosity and elastic properties of molded products, and through this, it is possible to achieve molded products with excellent physical properties, especially high elongation and softness. I can do it. Furthermore, when producing the latex composition for dip molding, if an epoxy crosslinking agent that binds to the carboxyl groups distributed within the latex particles is added, the physical properties will not change even if sterilized with gamma rays.

CV ₀ was measured using a Cannon-Fenske routine type (SI Analytics GmbH Type No. 520 13) capillary viscometer using methyl ethyl ketone (MEK) solvent at pH 8.2 to 9. It may be measured under the conditions of 2.

Equation 4 will be described below.
Regarding Equation 4 above, CV ₀ is as described in Equation 3. Further, CV _D indicates the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a deswelled state.

Deswelling (deswelling) means a state in which the part of the copolymer particles in the latex that has swelled in the methyl ethyl ketone solvent has been removed; for example, the copolymer particles in the latex in a swelled state A state in which a predetermined amount of energy is applied to remove the portion that dissolves in the methyl ethyl ketone solvent can be said to be in a deswelled state.

The CV _D was performed by dissolving the carboxylic acid-modified nitrile copolymer latex in a methyl ethyl ketone solvent under conditions of pH 8.2 to 9.2, and then using an ultrasonicator (Bransonic (registered trademark) M Mechanical Bath 5800). The capillary viscosity may be measured after deswelling the carboxylic acid-modified nitrile copolymer latex by applying 55 kcal to 65 kcal of energy for 40 minutes. At this time, the capillary viscosity can be measured using a Cannon-Fenske type capillary viscometer in the same manner as the CV ₀ measurement.

Moreover, the above-mentioned P is specifically the ratio of the capillary viscosity in the deswelled state to the capillary viscosity in the swelled state of the carboxylic acid-modified nitrile copolymer latex. The above P is 0.8 to 1. With such P, it is possible to obtain information about the latex particle structure such as entanglement, reluctance to unravel, and branching of the copolymer in the carboxylic acid-modified nitrile copolymer latex. A carboxylic acid-modified nitrile copolymer latex that satisfies the above range of P has a latex particle structure that has an appropriate level of copolymer entanglement and difficulty in unraveling, and is used as a latex composition for dip molding. In some cases, it can influence the optimization of the viscosity and elastic properties of the molded product, and dramatically improve the elasticity of the molded product, that is, the stress retention rate.

In this way, the latex of the present invention was completed by preparing the latex while checking the numerical ranges of CV ₀ and P. These latex properties make it possible to achieve optimal aluminum ion bonding and epoxy crosslinking when producing a latex composition for dip molding using an epoxy crosslinking agent and an aluminum crosslinking agent. This optimizes the viscosity and elastic properties of molded products manufactured using the latex composition for dip molding, resulting in molded products that are soft to the touch, have excellent wearing comfort, and elasticity.

(2) Epoxy crosslinking agent The epoxy crosslinking agent in the present invention has, for example, three or more glycidyl groups and an alicyclic, aliphatic, or aromatic parent skeleton in one molecule, and has an average number of epoxy groups of 2.25. , and the MIBK/water partition ratio is 50% or more.

Epoxy compounds are usually divided into monofunctional, bifunctional, and polyfunctional, but the crosslinking reaction occurs with bifunctional or more functional compounds, and among these, those with three or more glycidyl groups and the above-mentioned parent skeleton in one molecule are , is called a polyfunctional epoxy crosslinking agent.

Multifunctional epoxy crosslinking agents are usually produced as by-products at the same time, including difunctional and monofunctional, and therefore, except for pure reagents, they are mixtures of these. Therefore, in the present invention, a polyfunctional epoxy crosslinking agent having an average number of epoxy groups exceeding 2.25 may be used.

Incidentally, the average number of epoxy groups in the bifunctional epoxy crosslinking agent is about 1.5 to 1.8.

The average number of epoxy groups is determined by identifying the various epoxy compounds contained in the epoxy crosslinking agent by GPC, and multiplying the number of epoxy groups in one molecule of each epoxy compound by the number of moles of the epoxy compound. It is obtained by calculating the value for each epoxy compound and dividing the total value by the total number of moles of all epoxy compounds contained in the epoxy crosslinking agent.

Polyfunctional epoxy crosslinking agents, excluding by-products, have 3 or more glycidyl groups in one molecule and an alicyclic, aliphatic, or aromatic parent skeleton, so-called 3 or more glycidyl in 1 molecule. Examples of polyglycidyl ethers having groups include glycerol triglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane polyglycidyl ether, trimethylolethane triglycidyl ether, sorbitol triglycidyl ether, sorbitol tetraglycidyl ether, Examples include sorbitol polyglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether, pentaerythritol polyglycidyl ether, and diglycerol triglycidyl ether.

Further, the epoxy crosslinking agent in the present invention is, for example, a polyfunctional epoxy crosslinking agent having an average number of epoxy groups exceeding 2.25 and having an MIBK/water partition ratio of 50% or more.

The MIBK/water partition ratio is calculated when an epoxy crosslinking agent is mixed into a mixture of methyl isobutyl ketone (MIBK), which has the same hydrophobicity as a carboxylic acid-modified nitrile copolymer (hereinafter referred to as XNBR), and water. This is the percentage distributed to MIBK.

In the present invention, the MIBK/water partition ratio is more preferably 80% or more.

In the present invention, the latex composition for dip molding, the so-called dip liquid, is an alkaline water dispersion of XNBR particles, and the interior of the XNBR particles is a hydrophobic environment, while the space between the particles is a hydrophilic environment. This environment is almost the same as that of a mixed solution of MIBK and water. A high MIBK/water partition ratio means that more of the epoxy crosslinking agent enters the hydrophobic region within the XNBR particles and becomes stable. On the other hand, the epoxy crosslinking agent in the hydrophilic region of the dipping liquid undergoes rapid hydrolysis under alkaline conditions of about pH 10, and is deactivated within a relatively short period of time.

Conventionally, epoxy crosslinking agents have been used in water-based paints and solvent-based paints, but in both cases the crosslinking reaction takes place in a relatively short time due to evaporation, and the above-mentioned problems have not occurred.

When manufacturing gloves by dip molding, for example, when using an epoxy cross-linking agent while adding the maturation time and dipping liquid to the dip tank, it is necessary to keep the epoxy cross-linking agent from deactivating for at least 3 days. was there. Therefore, even if a bifunctional epoxy crosslinking agent or a polyfunctional epoxy crosslinking agent is used, it is preferable in dip molding if the MIBK/water partition ratio is 27% or more.

The more the MIBK/water distribution ratio of the polyfunctional epoxy crosslinking agent is 50% or more, the more the epoxy crosslinking agent is prevented from being deactivated within the XNBR particles, and the advantages of epoxy crosslinking can be exhibited.

The epoxy crosslinking agent became a crosslinking agent that could be used in dip molding for the first time due to the above selection. Epoxy crosslinking is characterized by high fatigue durability. On the other hand, the contribution to tensile strength was small, and it was necessary to add strength through ionic crosslinking such as zinc oxide.

In the present invention, attention was paid to the fact that most of the polyfunctional epoxy crosslinking agents having a high MIBK/water distribution ratio are contained in latex particles, which are hydrophobic regions.
This means that the epoxy crosslinking agent has the potential to increase the crosslinking density within the particles by covalently bonding with the carboxylic acid buried within the latex particles, thereby increasing the stress retention rate of the resulting film. For this purpose, it is necessary that the latex particles of the present invention have a structure that is appropriately entangled and difficult to unravel, and that there is an embedded carboxylic acid that binds to the epoxy crosslinking agent within the particles.

Most of the carboxyl groups in latex particles are present at the particle interface, and as the pH increases, they become oriented outward and take the form of carboxylate groups. These particles undergo interparticle crosslinking with metal crosslinking agents and some epoxy crosslinking agents during curing.

On the other hand, the carboxyl groups present within the particles are referred to as buried carboxylic acids, and the structure of the latex particles of the present invention ensures that the buried carboxylic acids crosslink within the particles with the epoxy crosslinking agent. Thus, by epoxy crosslinking the latex of the present invention, it can be imparted with stress retention.

Epoxy crosslinkers can be viewed as an alternative to sulfur vulcanization, which covalently bonds butadiene with sulfur.

In addition, unlike the above-mentioned carboxylic acid-modified nitrile copolymer, XNBR is particularly soft and has good elongation, epoxy crosslinking agents have a higher degree of deterioration in softness and elongation than other crosslinking agents even when crosslinked. was found to be low.

Furthermore, since epoxy crosslinking mainly enhances intraparticle crosslinking, even if products that require sterilization such as surgical gloves are irradiated with gamma rays, changes in basic physical properties such as tensile strength, elongation rate, and stress retention rate will not occur. It turned out to be small. This is considered to be due to the fact that the variation in physical properties due to the formation of crosslinks in the butadiene moieties within the particles due to γ-ray irradiation is small due to the enhancement of crosslinks within the particles due to the epoxy crosslinks within the particles.

The amount of the epoxy crosslinking agent added is preferably 0.1 parts by weight or more and 1.6 parts by weight or less, and 0.2 parts by weight or more based on 100 parts by weight of the elastomer, assuming that it is combined with a metal crosslinking agent. , more preferably 1.0 parts by weight or less. The epoxy crosslinking agent mainly performs intraparticle crosslinking, which is based on the premise that there is a carboxylic acid buried within the particles.

Note that the epoxy equivalent is also an important factor when considering the preferable range of the amount added. The molecular weight of an epoxy compound per epoxy group is called epoxy equivalent, which is obtained by dividing the molecular weight by the average number of epoxy groups (unit: g/eq.), and the equivalent weight of the epoxy crosslinking agent used in the present invention is 100 to 230 g/eq. eq. There is a range of For this reason, since the number of epoxy groups per unit weight varies depending on the type of epoxy crosslinking agent, the amount of epoxy crosslinking agent to be added should originally be considered on a molar basis, but in this specification, for convenience, it is on a weight basis.

When purchasing and obtaining the epoxy crosslinking agent according to the embodiment of the present invention, commercially available solvent-based epoxy crosslinking agents such as Denacol Ex-314, Ex-321, Ex-411, Ex-622 manufactured by Nagase ChemteX, etc. The following products can be mentioned.

Furthermore, many polyfunctional epoxy crosslinking agents with a high MIBK/water distribution ratio have conventionally been used mainly in oil-based paints and the like, and are difficult to dissolve in water. Therefore, it is preferable to dissolve it in a dispersant in advance before adding it to the latex composition for dip molding, which is a water/latex dispersion, and then mix it with the other components of the latex composition for dip molding. This is to quickly incorporate the epoxy crosslinking agent throughout the latex particles.

Examples of the dispersant for the epoxy crosslinking agent include monovalent lower alcohols, glycols, glycol ethers, and esters, but specifically methanol, ethanol, and diethylene glycol are preferably used, from the viewpoint of volatility and flammability. It is particularly preferred to use diethylene glycol.

The weight ratio of the epoxy crosslinking agent to the dispersing agent in the latex composition for dip molding is preferably 1:4 to 1:1.

(3) Aluminum crosslinking agent The aluminum crosslinking agent used in the present invention is preferably aluminum hydroxylate. Examples of aluminum hydroxy acids include aluminum glycolate, aluminum lactate, aluminum citrate, aluminum tartrate, aluminum malate, and aluminum gluconate. Among them, aluminum lactate is preferred because it has a small molecular weight, dissolves into water during the leaching process, and is unlikely to remain on gloves.

Carboxylic acid-modified nitrile copolymer latex generally has a pH of about 8.5, so when adding aluminum hydroxylate, which is acidic with a pH of 2 to 4, into a latex composition for dip molding, acid shock of the latex may occur. In order to prevent coagulation of the rubber component, it is preferable to adjust the pH to 7.0 or higher in advance with a hydroxide metal compound such as potassium hydroxide or a pH adjuster such as an ammonia aqueous solution.

The aluminum hydroxy acid contains at least a hydroxy acid ion and an aluminum ion, and may optionally contain other compounds.

The aluminum hydroxy acid can be produced by adding a hydroxy acid or a salt thereof to an aluminum salt, an aluminate salt, or a double salt thereof.

Aluminum salts include aluminum chloride hexahydrate, aluminum sulfate decahydrate, aluminum nitrate nonahydrate; aluminates include sodium aluminate and potassium aluminate; double salts thereof include potassium sulfate. Examples include aluminum dodecahydrate and ammonium aluminum sulfate dodecahydrate.

In the case of aluminate, acid shock does not occur because the pH is strongly basic.

The hydroxy acid for causing the above reaction is a compound having at least an alcoholic hydroxyl group and a carboxyl group in one molecule, and may optionally have other substituents. Examples of the hydroxy acids include glycolic acid, lactic acid, citric acid, tartaric acid, malic acid, gluconic acid, hydroxybutyric acid, hydroxyisobutyric acid, hydroxypropionic acid, and the like.

The advantages of using aluminum hydroxy acids in the present invention are described below.

First, the use of the aluminum hydroxylate provides stability to the aluminum cross-linking agent of the present invention by preventing gelation in a weakly alkaline region, allowing for long-term storage of the aluminum cross-linking agent and the use of dip-molded products using the aluminum cross-linking agent. enables the production of

In general, aluminum in water tends to gel (polymerize) in a weakly alkaline range (pH 7.0 to 11.0), and aluminum crosslinking agents have stability problems during long-term storage or during the manufacturing process of dip-molded products. exist. However, in the aluminum hydroxy acid, the aluminum ion and the carboxyl ion (carboxylate) of the hydroxy acid are strongly bonded, and the hydroxy acid sterically protects the aluminum, so that the gelation reaction can be prevented. Furthermore, the fact that the hydroxy acid has an alcoholic hydroxyl group has the effect of improving the affinity of the aluminum hydroxy acid with water and making it well dissolved and dispersed in water.

Second, since the aluminum hydroxylate reacts efficiently with the carboxyl group contained in the carboxylic acid-modified nitrile copolymer, the amount added can be reduced, and elution into the leaching solution during production can be suppressed. .

In addition, aluminum hydroxylate can reduce the incorporation of calcium into the molded product, which lowers the rubber elasticity of the molded product, thereby improving the rubber elasticity of the molded product. These are due to two types of reactions between the hydroxy acids and carboxylates, as shown below. The aluminum hydroxy acid undergoes an exchange reaction between the hydroxy acid and the carboxylate of XNBR in the latex composition for dip molding at room temperature, and a crosslinked structure is formed, so that the elution of the aluminum hydroxy acid during the leaching process is reduced. Furthermore, since the carboxylate of XNBR is already combined with aluminum when immersed in the latex composition for dip molding, the reaction between the calcium derived from the coagulant and the carboxylate of XNBR is suppressed. The aluminum hydroxylate forms a crosslinked structure with the carboxylic acid or carboxylate of XNBR during the curing process. When the aluminum hydroxy acid contains hydroxide ions, a crosslink is formed by a dehydration reaction. When the aluminum hydroxy acid contains unreacted hydroxy acid, it reacts with the carboxylic acid salt to form a crosslinked structure.

The carboxylate salt here may be a calcium salt, and can suppress calcium from being included in the molded product.

Based on the molar ratio of the hydroxy acid ions contained to the aluminum ions, it may be determined which of the two reactions the crosslinking reaction proceeds more. The molar ratio of hydroxy acid ions relative to aluminum ions is not particularly limited, but is preferably 0.5 or more and less than 3.0.

The details of the two types of crosslinking reactions are described below.

(i) Crosslinking reaction in latex composition for dip molding If the molar ratio of aluminum ions and hydroxy acid ions in the aluminum hydroxy acid is within the above-mentioned range, a hydroxy acid bonded to aluminum may be present. In addition, some carboxyl groups of the carboxylic acid-modified nitrile copolymer exist as carboxylate groups on the surface of the carboxylic acid-modified nitrile copolymer latex particles, and this and the hydroxy acid ion of the hydroxy acid aluminum can undergo an exchange reaction to form an aluminum crosslinker bonded to the rubber molecular chain. (See chemical formula 1 below)

In the above formula, RCOO ^- represents a hydroxy acid ion.

As shown in Chemical Formula 1, an exchange reaction is assumed in which the hydroxy acid bonded to the aluminum compound is released as a hydroxy acid ion, and aluminum is bonded to the carboxylate of XNBR. Through this reaction, the aluminum compound forms a bond with XNBR. This reaction starts in the latex composition for dip molding immediately after adding the aluminum crosslinking agent to the XNBR latex and is completed at room temperature.

(ii) Crosslinking reaction during curing step If the molar ratio of aluminum ions and hydroxyacid ions in the aluminum hydroxyacid is within the above-mentioned range, the aluminum crosslinking agent contains hydroxide ions. Therefore, a crosslinked structure can also be formed using the reaction mechanism described below. A latex composition for dip molding to which an aluminum crosslinking agent is added is formed into a film by a dip molding method. By washing this molded product with water in the leaching process, water-soluble impurities in the film are eluted, and at the same time, hydroxide metal compounds or ammonia compounds are also eluted, converting the carboxylate groups of XNBR into carboxyl groups. In the subsequent curing step, the molded product is heated and dried in a crosslinking furnace. During this curing process, the carboxyl groups of XNBR undergo a dehydration reaction with the hydroxide ions of the aluminum crosslinking agent, and the carboxyl groups of XNBR and aluminum bond to form a crosslinked structure. This reaction is shown in Chemical Formula 2.

Note that aluminum hydroxylate reacts with the calcium salt of carboxylic acid present during curing, and can reduce the calcium content. This improves the rubber elasticity of the molded product. This reaction is shown in Chemical Formula 3.

The aluminum crosslinking agent became a crosslinking agent that could be stably used in dip molding only by using the above aluminum hydroxy acid. Conventionally, zinc oxide has been mainly used as a metal crosslinking agent in dip molding. Zinc oxide has been used primarily to provide strength to molded bodies. In contrast, in recent years, aluminum crosslinking agents have been stabilized in latex compositions for dip molding, and can now be used as a substitute for zinc oxide. The above-mentioned aluminum hydroxy acid in the present invention is also one of them. In the present invention, the above aluminum hydroxy acid and an epoxy crosslinking agent are used together as a crosslinking agent in place of the conventional zinc oxide. The reason why the above aluminum hydroxy acid is used in place of zinc oxide will be explained while comparing the characteristics of zinc crosslinking and aluminum crosslinking.

Both zinc crosslinking and aluminum crosslinking create ionic bonds between particles and can maintain the strength of the molded product. However, the bonding strength of zinc crosslinks is weaker than that of aluminum, so it is easily cleaved by external force and recrosslinked with another carboxyl group, so the three-dimensional structure of the carboxylic acid-modified nitrile copolymer is not maintained, and the rubber Elasticity decreases. On the other hand, since aluminum crosslinking creates stronger bonds between particles, the stress retention rate can be dramatically increased.

Further, as mentioned above, aluminum hydroxylate has the effect of reducing the calcium content, thereby further increasing the stress retention rate. This is the reason for using an aluminum crosslinker in the present invention.

Epoxy crosslinking is also the same in that it increases stress retention, but its effect is different from aluminum crosslinking in that intraparticle crosslinking increases the crosslink density within particles and increases stress retention.

On the other hand, both aluminum crosslinking and zinc crosslinking are the same in that they impair the softness and elongation of the molded product. Therefore, in order to obtain a soft and stretchable molded article, it is necessary to use the soft and stretchable carboxylic acid-modified nitrile copolymer of the present invention.

By using an aluminum crosslinking agent, the molded article of the present invention was able to replace zinc oxide, which is a toxic heavy metal and has a large burden on the natural environment and the human body. Zinc oxide is an excellent cross-linking agent, but it has various problems, such as the problem of leaching wastewater treatment during manufacturing, the problem of elution and transfer to food and precision equipment during use, and the problem of ash treatment during disposal. There is. On the other hand, aluminum is a light metal, has low toxicity, and is an element that is common in the human body and the environment, so it has the advantage of not causing the same problems as zinc oxide.

Additionally, aluminum crosslinkers, unlike zinc oxide, can improve fatigue durability. This is because the ionic bond strength between aluminum ions and carboxyl groups is higher than that between zinc oxide and carboxyl groups.

This is because aluminum has a higher valence and a shorter ionic radius than zinc, so it is thought that the ionic bond strength that forms a crosslinked structure according to Coulomb's law is stronger than that of zinc. For this reason, gloves crosslinked with aluminum have the least amount of elution in artificial sweat liquid compared to gloves crosslinked with calcium or zinc oxide. This means that aluminum crosslinked gloves are the most resistant to sweat when worn.

In the present invention, the amount of the aluminum crosslinking agent added to the latex composition for dip molding is expressed as the amount added in terms of aluminum oxide (Al ₂ O ₃ ) shown by the following formula 6. This is because we believe that it is important how many aluminum atoms are added to the aluminum cross-linking agent, and the purpose is to evaluate the effect of the aluminum cross-linking agent regardless of the content of hydroxy acid ions, etc. .

In the above formula, the aluminum content was measured by ICP-AES.

The content ratio of the aluminum crosslinking agent in the latex composition for dip molding of the present invention is preferably from 0.1 parts by weight to 0.7 parts by weight, more preferably from 0.1 parts by weight to 0.7 parts by weight in terms of aluminum oxide, based on 100 parts by weight of the elastomer. It is 0.2 part by weight or more and 0.7 part by weight or less. If the content of the aluminum crosslinking agent is less than 0.1 part by weight, sufficient interparticle crosslinking will not be obtained, resulting in poor tensile strength of the molded product, and if the content is less than 0.7 part by weight, If the amount is more than 1, the thickening effect on the latex composition for dip molding becomes too large, and the resulting molded product becomes hard and difficult to stretch, contrary to the purpose of the present invention.

When purchasing and obtaining the aluminum crosslinking agent according to the embodiment of the present invention, examples of commercially available aluminum crosslinking agents include products such as Taxeram M-160L and AS800 manufactured by Taki Chemical Co., Ltd.

(4) Effects of combination So far, the latex, epoxy crosslinking agent, and aluminum crosslinking agent in the present invention have been explained respectively.

Here, we use SR modeling to analyze the factors that affect the viscosity and elastic properties of molded products, and how to improve softness by combining each element to complement each other and create a synergistic effect. We will explain whether it is possible to make molded products with (softness) and rubber elasticity.

SR Modeling can proceed in the following manner. SR manufactures dumbbell-shaped test pieces using the ASTM D-412 method, and uses a measuring device U.T.M (Instron, Model 3345) to measure the test pieces at a cross head speed of 300 mm/min and an elongation rate of 100%. This can be determined by measuring the stress reduction for 5 minutes after pulling the stress until it becomes . At this time, after reducing the magnification to 100%, the load values at 0, 4, 9, 19, 29, 49, 89, 169, and 289 seconds were measured, and a time-based load graph was created as the result. The values of k1, k2, and k3 can be obtained by fitting the thus obtained graph using the Maxwell-Weichert model of Equation 7 below.

F(t): Hourly load (N), t: Time (sec)
By dividing the k ₁ , k ₂ , and k ₃ values obtained in this way by the thickness of the test piece as shown in Equation 8 below, the final k ₁ ′, k ₂ ′, and k ₃ ′ values can be obtained. .

The Maxwell-Weichert model of Equation 7 is a model in which one elastic body and two viscoelastic bodies are connected in parallel. Therefore, the k ₁ , k ₂ , and k ₃ values obtained by data fitting the results obtained from the stress holding experiment using the Maxwell-Weichert model are divided by the thickness of the test piece. Among the obtained values of k ₁ ′, k ₂ ′, and k ₃ ′, k ₁ ′ is an index related to elastic physical properties, and k _{2 ′} and k ₃ ′ are indicators related to viscous physical properties.

Therefore, a molded article made from a latex composition for dip molding containing a carboxylic acid-modified nitrile copolymer latex that satisfies the following formulas 1 and 2 at the same time has optimized elastic and viscous properties, and is soft to the touch. Excellent wearability and elasticity.

As mentioned above, in the present invention, the latex is produced by controlling multiple factors such as the composition and polymerization method of the carboxylic acid-modified nitrile copolymer latex, and optimizing the molecular weight of the copolymer and the carboxyl group distribution within the latex particles. A latex with a structure that maximizes entanglement, resistance to unraveling, and degree of branching is created within the range of the latex, and later a latex composition for dip molding is manufactured using an aluminum crosslinking agent and an epoxy crosslinking agent. It is characterized by achieving the optimum degree of aluminum ion bonding and epoxy crosslinking in each case.

Under the structure of the latex, the epoxy crosslinking agent mainly covalently bonds with the carboxylic acid buried within the latex particles, thereby increasing the crosslinking density within the particles. The aluminum crosslinking agent firmly bonds particles in the structure of the latex to prevent them from shifting.

These different bonding methods of crosslinking agents have different effects on the elastic and viscous properties of molded products manufactured using these, and therefore the physical properties of molded products also differ depending on each crosslinking agent. . In other words, epoxy crosslinking is necessary to maintain the softness and stretchability of the latex itself, and aluminum crosslinking is necessary to maintain tensile strength and elasticity. This is because using only an epoxy crosslinking agent, the tensile strength and elasticity are unreliable, and using only an aluminum crosslinking agent results in hardness and short elongation. Therefore, it is necessary to find an optimal combination of crosslinking agents that uses epoxy crosslinking and aluminum crosslinking at the same time. This is possible when the sum of the amounts of crosslinking agents added is, for example, 0.2 parts by weight or more and 1.6 parts by weight or less, preferably 0.4 parts by weight or more and 1.4 parts by weight or less.

Then, it is possible to realize the combination of such crosslinking agents and the optimum degree of crosslinking. When a molded article is made from the latex described above, the molded article has optimal viscosity and elastic properties that simultaneously satisfy Formulas 1 and 2, producing gloves with good elasticity that meet the standards for surgical gloves. I was able to do that.

An epoxy crosslinker or an aluminum crosslinker alone can provide performance comparable to conventional XNBR gloves.

However, if the epoxy crosslinking agent alone is used, the interparticles will be weak, and if the aluminum crosslinker alone is used, the intraparticles will be weak. Therefore, the inventors believe that the epoxy crosslinked + aluminum crosslinked model is optimal as an alternative to the conventional sulfur vulcanized + zinc oxide crosslinked glove model. Furthermore, when a molded article is made from this crosslinked model and the latex, in its best embodiment, a glove that meets the standards for surgical gloves and has good rubber elasticity can be made.

Surgical gloves are usually sterilized by irradiation with gamma rays, but the physical properties of these gloves do not change much even after irradiation with gamma rays.

This is in contrast to the physical properties of crosslinked aluminum gloves that change significantly after γ-ray irradiation. The reason for this is thought to be that this glove is intraparticle crosslinked by epoxy crosslinking. The epoxy cross-linked + aluminum cross-linked model has the advantage that it does not cause type IV allergies caused by the vulcanization accelerator used in conventional sulfur vulcanization, and that it does not use zinc, which is a heavy metal.

2. Latex Composition for Dip Molding The latex composition for dip molding of the present invention is an aqueous dispersion containing at least the above-mentioned carboxylic acid-modified nitrile copolymer latex, an epoxy crosslinking agent, an aluminum crosslinking agent, water, and a pH adjuster. It is the body. This latex composition for dip molding serves as a raw material for making molded products such as gloves by dip molding.

A latex composition for dip molding is usually an aqueous emulsion in which water accounts for 60% or more (preferably 65 to 92% by weight).

It is preferable that the latex composition for dip molding is adjusted to have a pH of about 9.0 to 10.5 using a pH adjuster, and the solid contents are stirred and dispersed almost uniformly.

Hereinafter, other components that may be normally included in the pH adjuster and the latex composition for dip molding will be explained.

As the pH adjuster, ammonium compounds and alkali metal hydroxides can be used. Among these, potassium hydroxide (hereinafter also referred to as KOH) is most widely used because it is easy to adjust the pH.

The amount of the pH adjuster added can be about 0.1 to 4.0 parts by weight, but usually 0.1 to 4.0 parts by weight, based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer in the latex composition for dip molding. Use approximately 1 to 1.5 parts by weight.

The pH of the latex composition for dip molding is adjusted to, for example, 9.0 to 11.0, preferably 9.0 to 10.5. If the pH is 9.0 or higher, the orientation of the carboxylate groups on the particle surface will be sufficient, and there will be many bonds due to crosslinking, and the tensile strength will increase. Conversely, when the pH is less than 11.0, the orientation of the carboxylate groups on the particle surface is appropriate, the bonding through crosslinking is appropriate, and the softness and elongation are appropriate.

Further, for example, if the pH is set to about 8.0, the stress retention rate increases. As described above, pH is an important factor that influences the physical properties of a molded article.

The latex composition for dip molding may further contain a dispersant. As the dispersant, anionic surfactants are preferably used, and sulfonate salts are more preferably used.

Commercially available products can be used as the dispersant. For example, "Tamol NN9104" manufactured by BASF Corporation can be used. The amount used is preferably about 0.2 to 2.0 parts by weight per 100 parts by weight of the elastomer in the latex composition for dip molding.

The latex composition for dip molding can further contain various other additives. Examples of the additives include antioxidants, pigments, chelating agents, and the like. As the antioxidant, a hindered phenol type antioxidant, for example WingstayL, can be used. Further, as the pigment, for example, titanium dioxide is used. As the chelating agent, sodium ethylenediaminetetraacetate and the like can be used.

The latex composition for dip molding according to an embodiment of the present invention can be used not only for molding gloves, but also for medical supplies such as nipples for baby bottles, droppers, conduits, and water pillows, and toys such as balloons, dolls, and balls. Used in the molding of industrial products such as sports equipment, pressure molding bags, gas storage bags, etc., surgical, household, agricultural, fishing, and industrial gloves, finger cots, condoms, and other dip-molded products. Can be done.

3. Manufacturing method The molded article of the present invention can be produced by (i) a maturation step of preparing and stirring the latex composition for dip molding of the present invention, (ii) a dipping step of immersing a mold in the latex composition for dip molding; Gelling process to gel the film formed on the mold (iv) Leaching process to remove impurities from the film formed on the mold (v) Beading process to create windings at the ends (vi) Heating at high temperature It can be preferably manufactured by the following manufacturing method, which includes a curing step of drying and finally completing crosslinking to form a cured film as a molded product.
The details of each process will be explained below using gloves as an example of a molded product.

(i') Coagulant adhesion step This is the step of adhering a coagulant to the glove mold.
The mold or former (glove mold) is immersed in a coagulant solution containing, for example, 5 to 40% by weight, preferably 8 to 35% by weight, of Ca ²⁺ ions as coagulant and gelling agent. Here, the time for adhering the coagulant or the like to the surface of the mold or former is determined as appropriate, and is usually about 10 to 20 seconds. As a coagulant, calcium nitrate or chloride may be used. Other inorganic salts having the effect of precipitating the elastomer may also be used. Among these, it is preferable to use calcium nitrate. This coagulant is usually used as an aqueous solution containing 5 to 40% by weight.

Further, the solution containing a coagulant preferably contains potassium stearate, calcium stearate, mineral oil, ester oil, or the like as a mold release agent, for example, about 0.5 to 2% by weight, about 1% by weight.

Next, the mold or former with the coagulant solution adhered to it is placed in an oven with an internal temperature of about 110° C. to 140° C. for 1 to 3 minutes, and is dried to allow the coagulant to adhere to the entire or part of the surface of the glove mold. At this time, it should be noted that the surface temperature of the hand mold after drying is approximately 60°C, which will affect the subsequent reaction.

Calcium also serves not only as a coagulant to form a film on the surface of the glove mold, but also to crosslink a significant portion of the final glove.

In the present invention, in order to improve the physical properties of the glove, it is considered that excessive calcium should not be crosslinked, and the aluminum crosslinking agent has the advantage of being able to replace calcium crosslinking.

(i) Maturation step This is a step of preparing and stirring the latex composition for dip molding of the present invention.
When using an epoxy crosslinking agent and an aluminum crosslinking agent as in the present invention, there is no meaning in a pre-crosslinking step for aging as in conventional sulfur vulcanization.

The purpose of the present invention is to disperse and homogenize each component of the latex composition for dip molding through this step.

Another purpose is to adjust the pH of the dip-molding composition to, for example, 9.0 to 10.5.

In the actual glove manufacturing process, this maturation is usually carried out for about 1 to 2 days, and gloves are manufactured while replenishing the dip molding latex composition from the compound tank into the dip tank.
Therefore, it is important to stabilize the aluminum crosslinking agent without deactivating the epoxy crosslinking agent for at least 3 days, preferably about 5 days, while maintaining the pH.

(ii) Dipping step This is a step of dipping the glove mold into a latex composition for dip molding.
In the maturation step, the stirred latex composition for dip molding (dip liquid) according to the embodiment of the present invention is poured into a dip tank, and a coagulant is applied in the coagulant application step in the dip tank, and after drying. This is a process in which the mold or former is immersed for 10 to 40 seconds at a temperature of 25 to 35°C.

In this step, the calcium ions contained in the coagulant cause the elastomer contained in the latex composition for dip molding to aggregate on the surface of the mold or former to form a film.

(iii) Gelling process This is a process of gelling the film formed on the glove mold.
This is a process to gel the membrane to a certain extent to prevent it from deforming during the leaching process, and is usually carried out at 40°C to 120°C for 1 minute 30 seconds to 4 minutes during the manufacturing process. It will be held in The longer one is for double dipping. Sometimes it is heated in a gelling oven.

(iv) Leaching process This is a process of removing impurities from the film formed on the glove mold.
This is a process of washing with water to remove excess chemicals and impurities such as calcium deposited on the surface of the membrane that will interfere with subsequent curing. Normally, the former is soaked in warm water of 30 to 70 degrees Celsius for about 1 to 4 minutes.

In the leaching process, the membrane changes from alkaline to neutral by washing with water. Therefore, the carboxyl groups within the particles and the carboxylate groups oriented at the particle interface return to carboxyl groups. Then, the ratio of carboxyl groups within and between particles is determined here.

On the other hand, aluminum hydroxylates bonded to carboxylate groups do not flow out even when washed with water. In addition, surfactants, calcium derived from coagulants, and potassium derived from pH adjusters, which cause weakening of the physical properties of the gloves, flow out the more they are washed with water.

(v) Beading process This is the process of creating a wrap around the cuff of the glove.

This is a step of rolling up the cuff end of the glove, which has undergone the leeching process and has not yet been crosslinked, to create a ring of an appropriate thickness and reinforcing it. If it is carried out in a wet state after the leaching process, the adhesion of the roll portion will be good.

(vi) Curing process The curing process is a process of heating and drying at a high temperature to finally complete crosslinking to form a cured film as a glove.

Curing is carried out in multiple drying ovens, and the temperature of the first drying oven may be lowered slightly, but this can cause the moisture to evaporate rapidly and cause blistered protrusions on the gloves, resulting in poor quality. This is to prevent damage to the This is sometimes independently referred to as a precuring process. In this case, heating and drying are performed, for example, at 60 to 90° C. for about 30 seconds to 5 minutes.

Next, as a curing step, heating and drying are usually performed at 100 to 150° C. for about 15 to 30 minutes.

In this curing step, the OH of the carboxyl group and the aluminum hydroxy acid crosslink between the particles of XNBR, and the carbonyl group and the epoxy group of the carboxyl group within the particles of XNBR open the ring and crosslink. In addition, crosslinks of calcium derived from the coagulant, potassium derived from the pH adjuster, and carboxyl groups are also present in the glove.

(vi') Double dipping As for the glove manufacturing method, so-called single dipping has been described above. On the other hand, the dipping step and gelling step may be performed two or more times, and this is usually called double dipping.

Double dipping is performed when manufacturing thick gloves (film thickness of more than 200 to 300 μm) and also in the manufacturing method of thin gloves for the purpose of preventing the formation of pinholes.

One thing to note about double dipping is that in the second dipping process, sufficient time is required for the gelling process to allow calcium to sufficiently precipitate to the membrane surface in the first gelling process in order to aggregate XNBR. One example is that.

4. Gloves The XNBR gloves of the present invention are gloves that, even after being crosslinked with a crosslinking agent, have a high level of both softness and elasticity, which are not found in conventional XNBR gloves.

First, by controlling various factors in the composition and polymerization method of the carboxylic acid-modified nitrile copolymer latex, the molecular weight of the copolymer and the carboxyl group distribution within the latex particles are optimized to maximize entanglement within the range of the latex. We created a copolymer with a structure that improves entanglement and unraveling resistance. By simultaneously crosslinking such a copolymer with an epoxy crosslinking agent that performs intraparticle crosslinking and an aluminum crosslinking agent that performs interparticle crosslinking, optimal aluminum ion bonding and epoxy crosslinking are achieved. It has optimal viscosity and elastic properties.

As a result, in its best form, the resulting glove met the standards for surgical gloves and had a high stress retention rate not found in conventional XNBR gloves.

Surgical gloves usually require sterilization.

Gloves have various standards (JIS, ASTM, etc.) depending on various uses. Additionally, medical devices are classified as controlled medical devices depending on their use. Among these, sterilization is essential for surgical use, and sterilization is also required for pharmaceutical and dental use. Regarding sterilization, the Pharmaceutical and Medical Devices Act stipulates that the sterility guarantee level satisfies ^SAL10-6 (less than one product out of one million products has viable bacteria attached to it). Sterilization is generally performed by γ-ray irradiation. Irradiation takes about 3 hours at an absorbed dose of 25 kGy.

Surprisingly, the physical properties of the glove of the present invention crosslinked with epoxy and aluminum remained almost unchanged even after the above-mentioned γ-ray irradiation. Normally, when a substance is irradiated with gamma rays, it is divided into a collapsed type and a crosslinked type. Looking at XNBR, it is thought that butadiene has double bonds, and when irradiated, crosslinks are likely to be formed at the double bonds, which tends to cause changes in physical properties such as hardness.

For example, if the inside of the particle is not cross-linked, such as when aluminum is cross-linked alone, the physical properties will change significantly, but when used together with an epoxy cross-linking agent that cross-links inside the particle, the inside of the particle is already cross-linked, so the physical properties will change significantly. This is thought to be the reason for the small number. The characteristic of this glove that its physical properties do not change due to γ-ray irradiation is also favorable from the viewpoint of product stability.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the following examples are for illustrating the present invention, and it will be obvious to a person of ordinary skill in the art that various changes and modifications can be made within the scope and technical idea of the present invention. However, the scope of the present invention is not limited to this.

Example Example 1
<Production of carboxylic acid-modified nitrile copolymer latex>
In the following, weight percent is expressed based on the total monomer content added to form the main chain of the carboxylic acid-modified nitrile copolymer, and parts by weight are based on the total monomer content added to form the main chain of the carboxylic acid modified nitrile copolymer. The information is based on 100 parts by weight of the body.

After charging 23% by weight of acrylonitrile and 3.5% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed, and 0.6 parts by weight of t-dodecylmercaptan and 4.0 parts by weight of sodium dodecylbenzenesulfonate were added. After adding 120 parts by weight of water, 73.5 parts by weight of 1,3-butadiene was added, and 0.3 parts by weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.5 kgf/cm ² and a temperature of 40°C. Parts by weight were added to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.68 kgf/cm ² , the reaction pressure when the polymerization conversion rate is 60% is 3.55 kgf/cm ² , and the reaction pressure when the polymerization conversion rate is 90% was adjusted to 1.25 kgf/ ^cm2 .
When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

<Manufacture of latex composition for dip molding>
Trimethylolpropane polyglycidyl ether (epoxy crosslinking agent, Denacol Ex-321 manufactured by Nagase ChemteX Co., Ltd., epoxy equivalent: 140 g/equivalent, average 0.5 part by weight of epoxy group number 2.7, MIBK/water distribution ratio 87% was mixed in advance with 0.5 part by weight of diethylene glycol and added. Furthermore, basic aluminum lactate (aluminum crosslinking agent, M-160L manufactured by Taki Chemical Co., Ltd., based on basic aluminum lactate whose composition formula is Al ₅ (OH) ₁₁ (CH ₃ CH(OH)COO) ₄ ) After adjusting the pH of the organic acid aluminum salt and its modified product to 8.5, 0.3 part by weight in terms of aluminum oxide was added. 1 part by weight of titanium oxide, a potassium hydroxide solution, and secondary distilled water were added thereto to obtain a latex composition for dip molding having a solid content concentration of 22% by weight and a pH of 9.8-10.

<Manufacture of molded products>
A 20% coagulant solution was prepared by mixing 20% by weight calcium nitrate, 79.5% by weight water, and 0.5% by weight wetting agent (Huntsman Corporation, Teric 320), and a hand-shaped The ceramic mold was immersed for 10 seconds, taken out, and dried at 100° C. for 3 minutes to apply a coagulant to the hand-shaped mold.

Next, the ceramic plate coated with the coagulant was immersed in the obtained latex composition for dip molding for 10 seconds, taken out, dried at 50°C for 2 minutes, and then immersed in warm water at 50°C for 2 minutes. Next, the ceramic plate was preheated at 70°C for 5 minutes, and then heated at 130°C for 30 minutes to crosslink the latex. The crosslinked dip-molded layer was taken out from the ceramic plate to obtain a film-like molded product.

Example 2
After charging 27% by weight of acrylonitrile and 3.5% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed, and 0.5 parts by weight of t-dodecylmercaptan and 3.0 parts by weight of sodium dodecylbenzenesulfonate were added. After adding 120 parts by weight of water, 69.5 parts by weight of 1,3-butadiene was added, and 0.24 parts by weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.5 kgf/cm ² and a temperature of 37°C. was added to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.70 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 3.58 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.27 kgf/ ^cm2 .

When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 3
After charging 18% by weight of acrylonitrile and 4.5% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.3 parts by weight of t-dodecylmercaptan and 3.0 parts by weight of sodium dodecylbenzenesulfonate. After adding 130 parts by weight of water, 77.5% by weight of 1,3-butadiene was added, and 0.25 weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.7 kgf/cm ² and a temperature of 40°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.92 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 4.27 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.76 kgf/ ^cm2 .

When the polymerization conversion rate reached 96%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 4
After charging 28% by weight of acrylonitrile and 2.5% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.8 parts by weight of t-dodecylmercaptan and 3.0 parts by weight of sodium dodecylbenzenesulfonate. After adding 110 parts by weight of water, 69.5% by weight of 1,3-butadiene was added, and 0.35 weight of potassium persulfate, which is a polymerization initiator, was added at a pressure of 2.2 kgf/cm ² and a temperature of 37°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.38 kgf/cm ² , the reaction pressure when the polymerization conversion rate is 60% is 3.17 kgf/cm ² , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.76 kgf/ ^cm2 .

When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 5
After charging 25% by weight of acrylonitrile and 4.1% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started to mix and obtain 0.3 parts by weight of t-dodecylmercaptan and 2.5 parts by weight of sodium dodecylbenzenesulfonate. , 140 parts by weight of water was added, 70.9% by weight of 1,3-butadiene was added, and 0.2 weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.4 kgf/cm ² and a temperature of 40°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.52 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 3.12 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 0.24 kgf/ ^cm2 .

When the polymerization conversion rate reached 96%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 6
After charging 21% by weight of acrylonitrile and 2.9% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.6 parts by weight of t-dodecylmercaptan and 3.5 parts by weight of sodium dodecylbenzenesulfonate. After adding 110 parts by weight of water, 76.1% by weight of 1,3-butadiene was added, and 0.3 weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.6 kgf/cm ² and a temperature of 39°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.86 kgf/cm ² , the reaction pressure when the polymerization conversion rate is 60% is 4.29 kgf/cm ² , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 2.34 kgf/ ^cm2 .

When the polymerization conversion rate reached 95%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 7
After charging 28% by weight of acrylonitrile and 4.5% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.25 parts by weight of t-dodecylmercaptan and 3.0 parts by weight of sodium dodecylbenzenesulfonate. After adding 110 parts by weight of water, 67.5% by weight of 1,3-butadiene was added, and 0.45 weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.0 kgf/cm ² and a temperature of 36°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.2 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 2.6 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.8 kgf/ ^cm2 .

When the polymerization conversion rate reached 97%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 8
After charging 18% by weight of acrylonitrile and 2.5% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.5 parts by weight of t-dodecylmercaptan and 3.5 parts by weight of sodium dodecylbenzenesulfonate. After adding 120 parts by weight of water, 79.5% by weight of 1,3-butadiene was added, and 0.15 weight of potassium persulfate, which is a polymerization initiator, was added at a pressure of 2.8 kgf/cm ² and a temperature of 41°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 2.94 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 4.62 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 0.14 kgf/ ^cm2 .

When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Example 9
After charging 26% by weight of acrylonitrile and 4.0% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.6 parts by weight of t-dodecylmercaptan and 3.5 parts by weight of sodium dodecylbenzenesulfonate. After adding 120 parts by weight of water, 70% by weight of isoprene was added, and 0.3 parts by weight of potassium persulfate as a polymerization initiator was added at a pressure of 2.4 kgf/cm ² and a temperature of 41°C to emulsify. Polymerization started.

The reaction pressure when the polymerization conversion rate is 40% is 2.57 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 3.43kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.32 kgf/ ^cm2 .

When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Comparative example Comparative example 1
After charging 4.0 parts by weight of sodium dodecylbenzenesulfonate and 120 parts by weight of water into a polymerization reactor equipped with a stirrer, stirring was started and the mixture was mixed to obtain 29% by weight of acrylonitrile, 5.0% by weight of methacrylic acid, and t- After adding 0.6 parts by weight of dodecyl mercaptan, 66.0 parts by weight of 1,3-butadiene was added, and 0.6 parts by weight of potassium persulfate, a polymerization initiator, was added at a pressure of 2.5 kgf/cm ² and a temperature of 40°C. Emulsion polymerization was started by adding 3 parts by weight.
The reaction pressure when the polymerization conversion rate is 40% is 2.68 kgf/cm ² , the reaction pressure when the polymerization conversion rate is 60% is 3.55 kgf/cm ² , and the reaction pressure when the polymerization conversion rate is 90% was adjusted to 1.25 kgf/ ^cm2 .

When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Comparative example 2
After charging 25% by weight of acrylonitrile and 4.1% by weight of methacrylic acid into a polymerization reactor equipped with a stirrer, stirring was started and mixed to obtain 0.3 parts by weight of t-dodecylmercaptan and 2.5 parts by weight of sodium dodecylbenzenesulfonate. After adding 140 parts by weight of water, 70.9% by weight of 1,3-butadiene was added, and 0.2 weight of potassium persulfate, a polymerization initiator, was added at a pressure of 3.5 kgf/cm ² and a temperature of 40°C. to start emulsion polymerization.
The reaction pressure when the polymerization conversion rate is 40% is 4.06 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 4.13kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 3.71 kgf/ ^cm2 .

When the polymerization conversion rate reached 96%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Comparative example 3
After charging 4.0 parts by weight of sodium dodecylbenzenesulfonate and 110 parts by weight of water into a polymerization reactor equipped with a stirrer, stirring was started and the mixture was mixed to obtain 17% by weight of acrylonitrile, 2.0% by weight of methacrylic acid, and t- After 0.25 parts by weight of dodecyl mercaptan was added, 81.0 parts by weight of 1,3-butadiene was added, and 0.25 parts by weight of potassium persulfate, a polymerization initiator, was added at a pressure of 3.3 kgf/cm ² and a temperature of 41°C. Emulsion polymerization was started by adding 45 parts by weight.
The reaction pressure when the polymerization conversion rate is 40% is 3.89 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 5.68 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 3.03 kgf/ ^cm2 .

When the polymerization conversion rate reached 97%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Comparative example 4
After putting 4.0 parts by weight of sodium dodecylbenzenesulfonate and 120 parts by weight of water into a polymerization reactor equipped with a stirrer, stirring was started and the mixture was mixed to obtain 29% by weight of acrylonitrile, 2.0% by weight of methacrylic acid, and t- After 0.6 parts by weight of dodecyl mercaptan was added, 69.0 parts by weight of 1,3-butadiene was added, and 0.6 parts by weight of potassium persulfate, a polymerization initiator, was added at a pressure of 1.8 kgf/cm ² and a temperature of 41°C. Emulsion polymerization was started by adding 3 parts by weight.
The reaction pressure when the polymerization conversion rate is 40% is 2.02 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 3.02 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.69 kgf/ ^cm2 .

When the polymerization conversion rate reached 94%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Comparative example 5
After charging 4.0 parts by weight of sodium dodecylbenzenesulfonate and 140 parts by weight of water into a polymerization reactor equipped with a stirrer, stirring was started and the mixture was mixed to obtain 17% by weight of acrylonitrile, 5.0% by weight of methacrylic acid, and t- After adding 0.25 parts by weight of dodecyl mercaptan, 78.0 parts by weight of 1,3-butadiene was added, and 0.25 parts by weight of potassium persulfate, a polymerization initiator, was added at a pressure of 1.7 kgf/cm ² and a temperature of 36°C. Emulsion polymerization was started by adding 45 parts by weight.
The reaction pressure when the polymerization conversion rate is 40% is 1.96 kgf/ ^cm2 , the reaction pressure when the polymerization conversion rate is 60% is 2.16 kgf/ ^cm2 , and the reaction pressure when the polymerization conversion rate is 90%. was adjusted to 1.65 kgf/ ^cm2 .

When the polymerization conversion rate reached 97%, the polymerization was stopped. Thereafter, unreacted substances were removed by a deodorizing step, and aqueous ammonia, an antioxidant, and an antifoaming agent were added to obtain a carboxylic acid-modified nitrile copolymer latex.

Using the latex thus obtained, a dip-molded product was produced in the same manner as in Example 1.

Experimental example <Experimental example 1>
The physical properties of the carboxylic acid-modified nitrile copolymer latex prepared in the Examples and Comparative Examples were measured by the following method and are shown in Table 1 below.

(1) Capillary viscosity (mm ² /s, CV ₀ ): Each carboxylic acid-modified nitrile copolymer latex with a solid content of 44% to 46% was adjusted to pH 8.8 to 9.0 using 10% aqueous ammonia. 1 and then dissolved in methyl ethyl ketone (MEK) at a concentration of 2.55% by weight and uniformly dispersed. Next, inject 10 ml into a Cannon-Fenske routine type (SI Analytics GmbH Type No. 520 13) capillary viscometer, measure the time it takes to pass through the capillary at 25°C, and calculate the following formula. 9 was used to calculate the viscosity.

In Equation 9, k is a capillary constant (mm ² /s ² ), and t is the time taken to pass through the capillary (s).

(2) CV _D (mm ² /s), P: Each carboxylic acid-modified nitrile copolymer latex with a solid content of 44% to 46% was adjusted to pH 8.8 to 9.1 using 10% ammonia water. After adjusting the concentration to 2.55% by weight, it was dissolved in methyl ethyl ketone (MEK) and uniformly dispersed. Next, an ultrasonicator (Bransonic® M Mechanical Bath 5800) was used to apply 55 kcal to 65 kcal of energy for 40 minutes for deswelling, followed by Cannon-Fenske routine type, SI Analytics. 10 ml was injected into a capillary viscometer manufactured by GmbH Type No. 520 13), the time required for it to pass through the capillary at 25°C was measured, and the viscosity was calculated using Equation 1 above. Furthermore, P was measured by calculating the CV _D /CV ₀ .

The physical properties of the molded products manufactured in the Examples and Comparative Examples were measured by the following methods and are shown in Table 1 below.

(3) Tensile strength (MPa): According to ASTM D-412 method, measuring equipment U. T. M (manufactured by Instron, model 3345), the test piece was stretched at a crosshead speed of 500 mm/min, and then the point at which the test piece was cut was measured and calculated using the following equation 10.

(4) Elongation rate (%): According to ASTM D-412 method, measuring equipment U. T. M (manufactured by Instron, model 3345), the test piece was pulled at a crosshead speed of 500 mm/min, and then the point at which the test piece was cut was measured and calculated using Equation 11 below.

(5) 500% modulus (MPa): According to ASTM D-412 method, measuring equipment U. T. M (manufactured by Instron, model 3345), the crosshead speed was set to 500 mm/min, and the stress was measured when the elongation rate was 500%.

(6) Stress retention rate (%): A dumbbell-shaped test piece was prepared according to the ASTM D-412 method, and a measuring device U. T. M (manufactured by Instron, model 3345), the test piece was stretched at a crosshead speed of 300 mm/min until the elongation rate was 100%, and then the decrease in stress was measured for 5 minutes, and according to the following equation 12. I calculated it.

(7) _k1 ', _k2 ', _k3 ' (N/mm)
A dumbbell-shaped test piece was prepared according to the ASTM D-412 method, and a measuring device U. T. M (manufactured by Instron, model 3345), the test piece was pulled at a crosshead speed of 300 mm/min until the elongation rate was 100%, and then 0, 4, 9, 19, 29, 49, 89, 169 , the load value at 289 seconds was measured, and a time-based load graph was obtained as the result. The values of k ₁ , k 2 , and k ₃ can be determined by fitting the graph obtained in this manner using the Maxwell-Weichert model (FIGS. 1 and ₂ ) expressed by Equation 7 below. In FIG. 1, each square point indicates the load value at 0, 4, 9, 19, 29, 49, 89, 169, and 289 seconds, and the curve connecting each square point is the Maxwell - This is a line fitted using the Maxwell-Weichert model.

F(t): Hourly load (N), t: Time (sec)
By dividing the k ₁ , k ₂ , and k ₃ values obtained in this way by the thickness of the test piece as shown in Equation 8 below, the final k ₁ ′, k ₂ ′, and k ₃ ′ values can be obtained. .

The following abbreviations were used in the table.
BD: 1,3-butadiene
isoprene: isoprene
AN: Acrylonitrile
MAA: methacrylic acid

Referring to Table 1 above, Experiment No. 1 using the carboxylic acid-modified nitrile copolymer latex according to the present invention. In Nos. 1 to 9, CV ₀ was controlled to be 1.0 mm ² /s or more and 3.0 mm ² /s or less, and it was confirmed that P was 0.8 or more and 1 or less.

In comparison, experiment no. In the case of Comparative Examples 10 to 14, it was confirmed that either CV ₀ or P was outside this range.

Further, referring to Table 1, the carboxylic acid-modified nitrile copolymer latex of the present invention has a CV _of 1.0 mm ² /s or more and 3.0 mm ² /s or less, and P of 0.8 or more and 1 or less. A molded article dip-molded by making a dip-molding latex composition containing an aluminum crosslinking agent and an epoxy crosslinking agent has k ₁ '+k ₂ '+k ₃ ' of 9.3 N/mm or less, k ₁ '/(k ₁ '+ _k2 '+ _k3 ') was confirmed to be in the range of 0.55 or more.

Referring to Table 1 above, the dip according to the present invention in which k _{1 ′} +k ₂ ′+k ₃ ′ is 9.3 N/mm or less and k ₁ ′/(k _{1 ′} +k ₂ ′+k ₃ ′) is 0.55 or more It was confirmed that the molded product had a high stress retention rate and excellent elasticity, and also had a low 500% modulus, was flexible, and had an excellent wearing feeling.

<Experiment example 2>
In this Experimental Example 2, except for changing the amounts of the carboxylic acid-modified nitrile copolymer latex (XNBR latex) produced in Examples 5, 6, 7, and 8 of the present invention, the epoxy crosslinking agent, and the aluminum crosslinking agent. evaluated the physical properties of dip-molded products produced in the same manner as in Example 1.

As for the crosslinking agent, dip-molded products were produced using an epoxy crosslinking agent alone, an aluminum crosslinking agent alone, or a combination of the epoxy crosslinking agent of the present invention and an aluminum crosslinking agent while varying the amounts of each. Table 2 below shows the type of carboxylic acid-modified nitrile copolymer latex, the type and amount of crosslinking agent used, and the physical properties of the manufactured dip-molded product.

Referring to Table 2 above, the molded articles (Experiments Nos. 15 to 18) dip-molded using the dip-molding latex composition containing appropriate amounts of both an epoxy crosslinking agent and an aluminum crosslinking agent of the present invention had k ₁ ' + _k2 '+ _k3 ' is 9.3N/mm or less, _k1 '/( _k1 '+ _k2 '+ _k3 ') is 0.55 or more, and has a high stress retention rate and excellent elasticity. It was confirmed that the material had a low 500% modulus, was flexible, and had excellent wearing comfort.

Experimental example 3
In Experimental Example 3, the physical properties of dip-molded products produced in Example 2 of the present invention by changing only the amounts of the epoxy crosslinking agent and the aluminum crosslinking agent were evaluated. Furthermore, the physical properties of the dip-molded product were measured by irradiating it with gamma rays. The amount of crosslinking agent used and the physical properties of the dip-molded product are shown in Table 3 below.

Experiment No. Although No. 24 is an example without a crosslinking agent, it actually shows the physical properties of a calcium crosslinked product. This is considered to be the closest physical property to latex itself.
As you can see, this latex is very stretchy and soft as a starting point. It can be seen that although the stress retention rate is better than general latex, the latex itself does not have a particularly high stress retention rate. Also, the tensile strength is very low.

When this was irradiated with gamma rays, the tensile strength and stress retention rate increased, the elongation rate decreased, and the 500% modulus increased. Furthermore, fatigue durability has been significantly improved. From this, it can be understood that γ-ray irradiation significantly changes the physical properties of the film.
Next, experiment no. 25, only epoxy crosslinking, Experiment No. In No. 26, the physical properties of the film in which only aluminum was crosslinked were confirmed. Looking at this, it can be seen that aluminum crosslinking is better in terms of tensile strength, while epoxy crosslinking is inferior. Furthermore, it can be seen that while epoxy crosslinking does not significantly impair the softness and elongation of the latex itself, aluminum crosslinking makes the film less elongated and harder than epoxy crosslinking. It can be seen that both crosslinking agents greatly increase the stress retention rate of the latex itself. Furthermore, when it is irradiated with gamma rays, it becomes even harder than epoxy, especially in the case of aluminum crosslinking. This indicates that the physical properties of aluminum crosslinking deteriorate due to γ-ray irradiation.

After grasping the above trends, experiment No. The physical properties of the film were checked by varying the amounts of the epoxy crosslinking agent and the aluminum crosslinking agent from No. 27 to No. 28.
As a result, it was confirmed that all of the molded products were soft and stretchable, unlike conventional XNBR gloves, and had a high stress retention rate.
Among these, in consideration of the balance between physical properties, the optimal embodiment is the combined use of 0.5 parts by weight of an epoxy crosslinking agent and 0.3 parts by weight of an aluminum crosslinking agent (Experiment No. 28). Furthermore, this optimal embodiment was found not to be significantly affected after gamma irradiation.

The molded article of the present invention takes advantage of the inherent softness and elongation of the XNBR latex of the present invention, and also has a greatly increased stress retention rate due to the appropriately entangled structure of the XNBR latex of the present invention, and has stable physical properties even after irradiation with gamma rays. We were able to create a molded object that has never been seen before. Among these, it has been found that in the best form, it is possible to manufacture XNBR gloves that meet the standards for surgical gloves.

Experimental example 4
A latex composition for dip molding with a solid content concentration of 30% by weight and a pH of 8-11 was used instead of a latex composition for dip molding with a solid content concentration of 22% by weight and a pH of 9.8-10, and a latex composition for dip molding with a solid content concentration of 30% by weight and a pH of 8-11 was used instead of a 20% coagulant solution. A dip-molded article was produced in the same manner as in Example 1, except that a 30% coagulant solution was used. The 30% coagulant solution was prepared by mixing 30% by weight of calcium nitrate, 69.5% by weight of water, and 0.5% by weight of a wetting agent (Huntsman Corporation, Teric 320). pH changes were made using potassium hydroxide or hydrochloric acid as necessary. As the crosslinking agents, 0.5 parts by weight of each of an epoxy crosslinking agent and an aluminum crosslinking agent were added and kept constant. Furthermore, although the film thickness of the molded product film is shown in Table 4, a phenomenon occurred in which the film thickness increased as the pH decreased. The pH of the latex composition for dip molding and the physical properties of the obtained dip molded product are shown in Table 4 below.

From Table 4, it was confirmed that the higher the pH of the dip-molded latex composition, the higher the tensile strength of the dip-molded product. Furthermore, the lower the pH of the latex composition for dip molding, the better the elongation of the dip molded product, the lower the 500% modulus, and the softer it was. The stress retention rate of dip-molded products was best at pH 8.5 to 9.5. The physical properties of the dip-molded product exhibited the best balance when the dip-molded latex composition had a pH of 9.0 to 9.5.

Experimental example 5
In this Experimental Example 5, a latex composition for dip molding with a solid content concentration of 30% by weight and a pH of 9.5 was used instead of a latex composition for dip molding with a solid content concentration of 22% by weight and a pH of 9.8-10. A dip-molded product was produced in the same manner as in Example 1, except that a 30% coagulant solution was used instead of the coagulant solution, and crosslinking was performed with 0.5 parts by weight of an epoxy crosslinking agent and 0.7 parts by weight of an aluminum crosslinking agent. Experiment Nos. 36 to 40) and Experiment No. 1 except that crosslinking was performed using 0.8 parts by weight of an epoxy crosslinking agent and 0.4 parts by weight of an aluminum crosslinking agent. Each of the dip-molded products (Experiment Nos. 41 to 45) produced in the same manner as Examples 36 to 40 was irradiated with gamma rays, and changes in their physical properties were observed.

These molded products used a combination of aluminum crosslinking agent and epoxy crosslinking agent, but Experiment No. Experiment Nos. 36 to 40 have a large amount of aluminum crosslinking agent. Samples 41 to 45 contain a larger amount of epoxy crosslinking agent.

Although the commercially molded product of the present invention has physical properties that can be used as pharmaceutical gloves and surgical gloves, gamma ray sterilization is required to utilize it. In gamma ray sterilization, it is important that the gloves do not change due to gamma ray irradiation. Therefore, changes in the physical properties of the molded product were confirmed in the irradiation range of 0 to 100 kGy. Incidentally, the pH of the dip liquid was 9.5. Table 5 below shows changes in the physical properties of the molded product due to γ rays.

All molded products had the same tendency to decrease in elongation rate, increase in 500% modulus, and become harder as the γ-ray irradiation dose increased. Moreover, the tensile strength and stress retention rate were almost unchanged. However, the elongation rate and 500% modulus were determined by Experiment No. with a large amount of epoxy crosslinking agent. It was found that the rate of change was smaller for molded products numbered 41 to 45.
In the case of the usual γ-ray sterilization with an irradiation dose of 25 kGy, both molded products showed good physical properties even after irradiation. The physical properties of the two molded products in the case of 25 kGy were as follows: Experiment No. 1 using an epoxy crosslinking agent. It was found that molded products No. 41 to No. 45 were softer. Other physical properties were almost the same for all molded products.

Claims (6)

A dip-molded article comprising a layer derived from a latex composition for dip-molding,
The latex composition for dip molding includes a carboxylic acid-modified nitrile copolymer latex,
The carboxylic acid-modified nitrile copolymer latex includes a carboxylic acid-modified nitrile copolymer,
The dip-molded product has an elongation rate greater than 650% and has the following formulas 1 and 2,
The carboxylic acid-modified nitrile copolymer latex satisfies the following formulas 3 and 4,
The carboxylic acid-modified nitrile copolymer contains 18 to 28% by weight of units derived from ethylenically unsaturated nitrile monomers and conjugated diene monomers based on the dry weight of the carboxylic acid-modified nitrile copolymer. 67.5 to 79.5% by weight of units derived from the body and 2.5 to 4.5% by weight of units derived from ethylenically unsaturated acid monomers,
Dip molded products.

(In the above formula, k ₁ ' is the value obtained by dividing the equilibrium coefficient k ₁ by the thickness of the test piece, and k ₂ ' and k ₃ ' are the viscosity coefficient ( This is the value obtained by dividing k ₂ and k ₃ by the thickness of the test piece.)

(In the above formula, CV ₀ represents the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a swelled state, and CV _D represents the capillary viscosity of the carboxylic acid-modified nitrile copolymer latex in a deswelled state. (Indicates viscosity.) The dip-molded article according to claim 1 , wherein the dip-molded latex composition further contains an epoxy crosslinking agent and an aluminum crosslinking agent, as well as water and a pH adjuster. The amount of the epoxy crosslinking agent added is 0.1 to 1.6 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer, and
The amount of the aluminum crosslinking agent added is 0.1 to 0.8 parts by weight in terms of aluminum oxide based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer,
When both the epoxy crosslinking agent and the aluminum crosslinking agent are added, the total amount of the epoxy crosslinking agent and the aluminum crosslinking agent is 0.00 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer. The dip-molded product according to claim 2, wherein the amount is 2 to 1.6 parts by weight. The amount of the epoxy crosslinking agent added is 0.2 to 1.0 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer, and
The amount of the aluminum crosslinking agent added is 0.2 to 0.7 parts by weight in terms of aluminum oxide based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer,
When both the epoxy crosslinking agent and the aluminum crosslinking agent are added, the total amount of the epoxy crosslinking agent and the aluminum crosslinking agent is 0.00 parts by weight based on 100 parts by weight of the carboxylic acid-modified nitrile copolymer. The dip-molded product according to claim 2 , wherein the amount is 4 to 1.4 parts by weight. The epoxy crosslinking agent has three or more glycidyl groups and an alicyclic, aliphatic or aromatic parent skeleton in one molecule, the average number of epoxy groups exceeds 2.25, and the MIBK/water partition ratio is 50. % or more, and
the aluminum crosslinking agent is an aluminum hydroxy acid;
The dip-molded product according to any one of claims 2 to 4 . The carboxylic acid-modified nitrile copolymer latex according to claim 1 ;
an epoxy crosslinker;
A latex composition for dip molding containing at least an aluminum crosslinking agent.