JP2017095629A - High strength synthetic polyisoprene cross-linked body having flexibility and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic polyisoprene cross-linked body low in toxicity and excellent in mechanical properties, and substitutable for immersion products for medicine and hygiene using the conventional vulcanized natural rubber.SOLUTION: In a polyisoprene cross-linked body obtained by solidifying and cross-linking a composition obtained by adding specified organic peroxide and cross-linking agent to a synthetic polyisoprene latex, by-product is suppressed, and cross-linking reaction is progressed by performing the cross-linking in cross-linking reaction at relatively low temperature in an atmosphere in a substantially non-oxygen state. The obtained synthetic polyisoprene cross-linked body being the material excellent in high strength and high elongation while maintaining high flexibility, and being a composition with high safety solving I type and IV type allergy, N-nitrosoamine problems generated by the conventional natural rubber products since sulfur and vulcanization accelerators are not substantially contained.SELECTED DRAWING: None

Description

The present invention is a synthetic polyisoprene crosslinked body that is substantially free of sulfur and sulfur compounds and has excellent mechanical properties, and is a low-toxic synthetic polyisoprene composition that can replace conventional natural rubber products. It is an invention belonging to a medical and sanitary rubber immersion product that requires high safety in the raw material used.
That is, the present invention relates to a synthetic polyisoprene crosslinked body using an organic peroxide, and relates to a method for producing a synthetic polyisoprene crosslinked body characterized in that the crosslinking step is at a relatively low temperature and substantially oxygen-free. .

Soaking products such as gloves using natural rubber and natural rubber latex as raw materials have been widely used.
They have high physical strength, low elastic modulus and hardness, high elongation, and excellent physical properties not found in other elastomeric materials.
However, protein contained in natural rubber may cause type I rapid type allergy, and type IV delayed type allergy (hypersensitivity) due to a vulcanization accelerator compounded in vulcanized natural rubber. ) Was a problem.
Furthermore, there is a problem that a vulcanization accelerator composed of a secondary amine reacts with nitrogen oxides present in the air or nitrogen oxides remaining in rubber to produce carcinogenic N-nitrosamines, It was necessary to replace natural rubber products with health hazards caused by vulcanization accelerators and other materials that could come into contact with people.
On the other hand, in terms of performance, high strength, elasticity and flexibility are maintained, and excellent performance comparable to conventional natural rubber products is required. Therefore, no vulcanization accelerator is used and natural rubber is substituted. There has been a demand for a method for producing a soaked product using a synthetic elastomer suitable as the above.

Currently, many materials using synthetic elastomers have been developed. In particular, in the immersion molding, synthetic polyisoprene (IR), polychloroprene (CR), and acrylonitrile butadiene rubber (NBR) are mainly used. By using these as main raw materials, the type I allergy problem is solved.
Among them, it is expected to find performance comparable to natural rubber by using synthetic polyisoprene, which is the closest to the excellent performance (tensile strength, elongation rate, flexibility, texture) of natural rubber.
However, the compounding agent for immersion molding using synthetic polyisoprene as the main raw material contains a dithiocarbamate vulcanization accelerator and a thiazole vulcanization accelerator, which are conventionally used vulcanization accelerators. Is raised. (Patent Document 1)
In this case, there is a risk of causing type IV allergy and N-nitrosamine problems, and therefore there is a need for other crosslinking methods that do not use vulcanization accelerators.

In addition to crosslinking with sulfur and a vulcanization accelerator, as a typical crosslinking method, there is peroxide (peroxide) crosslinking using an organic peroxide, which is generally established as crosslinking of elastomer materials.
Peroxide cross-linking is relatively simple compared to cross-linking with sulfur and vulcanization accelerators, but the disadvantage is that depending on the half-life temperature of the peroxide used, the cross-linking reaction must be carried out at a high temperature. For this reason, the physical properties are disadvantageous in that they are hard and inferior in strength and flexibility because of their high modulus of elasticity compared to crosslinking with sulfur and a vulcanization accelerator.
Furthermore, the presence of oxygen during the reaction of peroxide crosslinking means that the generated radicals are combined with oxygen, and the main chain of the rubber is broken simultaneously with the crosslinking reaction. The crosslinking process is performed in hot air drying (air drying) in the presence of oxygen. Then, the surface was sticky and it was extremely difficult to produce a product.
Therefore, in peroxide crosslinking, it is essential to carry out under conditions where the amount of oxygen is low or in an oxygen-free state, and under conditions where the solid rubber is dissolved in an organic solvent without using latex, it is difficult to be affected by oxygen. A rubber having a butadiene unit that is easily reacted is added. (Patent Document 2)
In this case, since a large amount of an organic solvent is used, the working environment is bad and unsuitable for mass production.

On the other hand, there is a crosslinking method using a molten salt bath as an inert solvent in a deoxygenated state. (Patent Documents 3 and 4)
In these cases, the composition used is a synthetic polyisoprene latex, but the peroxide used in the reaction is dicumyl peroxide with a very high half-life temperature of 175 ° C. for 1 minute, and melted. The crosslinking reaction must be carried out at extremely high temperature conditions such as salt.
In addition, since the crosslinking temperature is generally appropriate to be performed within the range of about 20 ° C. of the one minute half-life temperature of the peroxide used, as long as a peroxide having a high half-life temperature is used, It is necessary to set a high crosslinking temperature.
In Patent Document 3, sulfur is added to increase strength and flexibility.
Therefore, by performing cross-linking with a molten salt, it is not affected by oxygen and the stickiness of the surface is suppressed, but in this case, special equipment is required, especially in the case of a production line that performs conventional immersion molding, Not suitable for mass production, the manufacturing process must be done in a simpler way.

In the case of using a synthetic polyisoprene latex and performing peroxide crosslinking without compounding sulfur or a vulcanization accelerator, benzoyl peroxide (130.0 ° C) having a relatively low one-minute half-life temperature of the peroxide And dilauroyl oxide (116.4 ° C) are used, but in this case, an aging step is required, and aging requires several steps and a long time. There is a possibility that the effective activity may be remarkably lowered, and since it is difficult to control the degree of crosslinking, there is a concern that the physical properties of the finished product are likely to vary.
In the post-vulcanization, there is a process of heating at a relatively high temperature of 120 ° C., and since it is performed by hot air drying in an oxygen atmosphere, surface stickiness is likely to occur.
Moreover, since no cross-linking agent is used in combination, the finished product has a low elongation rate and low strength and is poor in flexibility. (Patent Documents 5 and 6)

Therefore, in the peroxide crosslinking of synthetic polyisoprene latex that does not use sulfur and a vulcanization accelerator, as described above, no special equipment is required, and a simple and low-cost production method provides excellent stability with a low degree of crosslinking. There is a need to obtain a synthetic polyisoprene having excellent physical properties.

JP-T-2004-532752 JP-A-8-10317 Special table 2006-502024 gazette Special table 2011-67636 gazette JP 2006-321955 A International Publication Number WO2006-057392

The present invention is a synthetic polyisoprene crosslinked body that is substantially free of sulfur and a vulcanization accelerator and is composed of a low-toxicity material, and has excellent mechanical properties with stable quality by a simple and inexpensive manufacturing process. The objective is to provide the material that is suitable for medical and sanitary rubber dipping products.
In other words, peroxide crosslinking using synthetic polyisoprene latex is performed, and it is possible to obtain a stable physical property of the degree of crosslinking without requiring an aging step by a simple production method. By carrying out under a low temperature and substantially oxygen-free atmosphere, side reactions are suppressed, maintaining high flexibility that could not be realized with the prior art, and making it possible to obtain a high-strength polyisoprene crosslinked product. .

In order to solve the above-described problems, the present inventor has intensively studied, and as a result, has found that the problem is solved by the following configuration.
As a first invention in the present invention, as described in claims 1 and 2,
The composition comprising the synthetic polyisoprene latex (S-0) is solidified and cross-linked, and is a synthetic polyisoprene cross-linked product (X).
The strength at break (TS) is 15 MPa or more, and
Satisfy at least two of the following mathematical formulas (1) to (3),
A synthetic polyisoprene crosslinked product (X) characterized in that the amount of sulfur element is 500 ppm or less,

Furthermore, it is synthetic polyisoprene crosslinked body (X ') of Claim 1 which satisfy | fills all among following numerical formula (4)-(6).

As a second invention,
Synthetic polyisoprene latex (S-0);
A composition comprising an organic peroxide having a one-minute half-life temperature of 100 ° C. to less than 120 ° C .;
The synthetic polyisoprene solid (S-1) from which the moisture of the composition was removed was
By performing crosslinking at a crosslinking temperature of less than 120 ° C,
A synthetic polyisoprene crosslinked product (S-2) characterized by satisfying claims 1 and 2 and a method for producing the same.
In particular, when a crosslinking agent is used in combination with an organic peroxide, the effect is more remarkable, and a polyfunctional (meth) acrylate, a silane coupling agent having a double bond or a thiol group is suitable as the crosslinking agent. .

Synthetic polyisoprene that satisfies the above conditions does not contain natural rubber-derived proteins or vulcanization accelerators, uses specific organic peroxides that are easy to store and handle, and has low toxicity. Realized to get a body.
The manufacturing process does not require a long process such as aging, and is performed in a deoxidized state such as a crosslinking process at a relatively low temperature and an inert gas atmosphere or a water bath substituted with an inert gas. By improving the simple apparatus, it is possible to manufacture with a conventional immersion molding line.
In particular, by performing the crosslinking reaction at a relatively low temperature, it is possible to obtain a synthetic polyisoprene crosslinked body satisfying claims 1 and 2.

The synthetic polyisoprene cross-linked product obtained by the present invention realizes excellent physical properties of high strength and high elongation, maintaining high flexibility.
The present invention is suitable for immersion products such as balloons and gloves that require high stretchability, and is particularly useful for rubber products in the medical field.

The present invention is described in detail below.
The synthetic polyisoprene crosslinked product (X) according to the first aspect of the present invention is as described in claim 1.
A synthetic polyisoprene latex (X) obtained by using a synthetic polyisoprene latex (S-0) as a raw material, solidifying and crosslinking a composition containing the latex,
The cross-linked product (X) is sheeted to a thickness of about 1 mm, and measured according to a method based on JIS K6251 using a No. 4 dumbbell at a speed of 500 mm / min.
The strength at break (TS) is 15 MPa or more, and
Satisfy at least two of the following mathematical formulas (1) to (3),
A synthetic polyisoprene crosslinked product (X) characterized in that the amount of sulfur element is 500 ppm or less,

Furthermore, as described in claim 2,
The synthetic polyisoprene crosslinked product (X ′) according to claim 1, wherein all of the following formulas (4) to (6) are satisfied.

The synthetic polyisoprene crosslinked products (X) and (X ′) satisfying the above conditions are surprisingly high-strength strength, stretchable, and very soft materials.
Therefore, the physical properties in the present invention include (1) high strength at break (2) high elongation (3) low elastic modulus, and represents the mechanical properties of the synthetic polyisoprene crosslinked product obtained in the present invention, In order to parameterize the physical properties (1) to (3), parameters shown in the following formula (A) were created.

Surprisingly, it was found that the synthetic polyisoprene crosslinked product of the present invention satisfies the following conditions in terms of mechanical parameter values (Ω).
That is, the dynamic parameter value (Ω) is
(A) When M = 300M, Ω value (300M) ≧ 175
(B) When M = 500M, Ω value (500M) ≧ 100
(C) When M = 700M, Ω value (700M) ≧ 40
It is essential to satisfy at least two of (a) to (c), and it has been found that the synthetic polyisoprene crosslinked product obtained in this patent satisfies them.
It is essential that the strength at break (TS) of the crosslinked synthetic polyisoprene is 15 MPa or more.

In Ω value at each elastic modulus,
(A) The Ω value (300M) must be Ω ≧ 175, more preferably Ω ≧ 200, more preferably Ω ≧ 225, and most preferably Ω ≧ 250,
(B) As for the Ω value (500 M), Ω ≧ 100 is essential, more preferably Ω ≧ 120, more preferably Ω ≧ 150, most preferably Ω ≧ 175,
(C) The Ω value (700M) is Ω ≧ 40, more preferably Ω ≧ 50, more preferably Ω ≧ 75, and most preferably Ω ≧ 100.
It is essential to satisfy at least two of (a) to (c), but most preferably, all of (a) to (c) are satisfied.
When the Ω value at each elastic modulus is less than the specified value, the balance between the strength at break, the elongation rate, and the elastic modulus is bad, which is not preferable.

In the synthetic polyisoprene crosslinked body in which the mechanical properties are highly balanced, by defining the mechanical parameter value Ω obtained from the mathematical formula (A), the optimum balance of strength at break, elastic modulus and elongation rate is recognized, This value can be derived and is a suitable parameter for unifying performance that requires high flexibility and strength.
The breaking strength is essential to be 15 MPa or more, preferably 17.5 MPa or more, more preferably 20 MPa or more, more preferably 22 MPa or more, still more preferably 24 MPa or more, and most preferably 27 MPa or more.
When the strength at break is less than 15 MPa, the strength is insufficient, and there is a risk of bursting during use, such being undesirable.

The amount of elemental sulfur specified in claim 1 is essential from the viewpoint of not containing a sulfur compound derived from a vulcanization accelerator, so that it is essential not to substantially contain sulfur and a sulfur compound. In claim 1, the content of elemental sulfur is defined as 500 ppm or less.
In addition, the sulfur element amount prescribed | regulated here is a value when it measures using a fluorescent X-ray apparatus.
Some of them are values measured using an ICP device and a calibration curve is obtained between them.
The sulfur content in claim 1 is essential to be 500 ppm or less, preferably 250 ppm or less, more preferably 100 ppm or less, still more preferably 50 ppm or less, and most preferably below the detection limit.
If the sulfur content exceeds 500 ppm, it may exceed the specified value by containing a sulfur compound vulcanization accelerator, which may cause the onset of type IV allergy and N-nitrosamine problems. It is not preferable because it tends to have high elasticity and high hardness, lacking flexibility in mechanical properties.
The regulation of the sulfur content is that, in addition to the sulfur compound from which the vulcanization accelerator is derived, a commercially available compounding agent (surfactant, etc.) of synthetic polyisoprene latex contains a sulfur element-containing compound. In addition, as described above, the amount of elemental sulfur was defined for distinction from a thiol group-containing silane coupling agent used as a crosslinking agent, which will be described later.

The characteristics of the excellent physical properties of the above-mentioned synthetic polyisoprene crosslinked body will be described in more detail.
As claimed in claim 2,
The synthetic polyisoprene crosslinked product (X ′) according to claim 1, wherein all of the following formulas (4) to (6) are satisfied.

in this case,
(1) As a high strength at break,
It is essential that the strength at break is 20 MPa or more, more preferably 22 MPa or more, still more preferably 24 MPa or more, and most preferably 27 MPa or more.
When the strength at break is less than 20 MPa, the strength is insufficient, and there is a risk of bursting during use, such being undesirable.
(2) As a high elongation rate,
The elongation rate is essential to be 900% or more, more preferably 1000% or more, and most preferably 1100% or more.
If it is less than 900%, it is not preferred because it lacks flexibility.
(3) As a low elastic modulus,
In the 300M value, 1.1 MPa or less is essential, more preferably 1.05 MPa or less, still more preferably 1.0 MPa or less, and most preferably 0.9 MPa or less.
If it is 1.10 MPa or less, the elastic modulus is about the same as or lower than that of sulfur vulcanized natural rubber, and the same feel as that of sulfur vulcanized natural rubber can be obtained in flexibility. When it exceeds 1.10 MPa, the elastic modulus becomes high and the touch feeling is hard, which is not sensibly preferable.
In the 500M value, 1.9 MPa or less is preferable, more preferably 1.75 MPa or less, and most preferably 1.5 MPa or less.
If it is 1.9 MPa or less, the elastic modulus is the same as or lower than that of the sulfur vulcanized natural rubber, and a softness equivalent to that of the sulfur vulcanized natural rubber can be obtained.
If it exceeds 1.9 MPa, it becomes highly elastic and the feel of touch is hard, which is undesirably sensual.
The 700 M value is not particularly problematic as long as it satisfies claim 1, but if it is 7 MPa or more, the feeling of touch is hard and not preferred.
The pressure is preferably 5 MPa or less, particularly preferably 4 MPa or less, and most preferably 3.5 MPa or less.
In the conventional peroxide cross-linking of synthetic polyisoprene, the synthetic polyisoprene cross-linked product at a high cross-linking temperature of 120 ° C. or higher has a mechanical property parameter value (Ω) of 2 of (a), (b) and (c). There was nothing to satisfy more than one.

The measurement of the crosslinking density in the synthetic polyisoprene crosslinked body is calculated by the degree of swelling.
The degree of swelling was determined by immersing the synthetic polyisoprene crosslinked body in a non-polar solvent such as toluene for 24 hours and calculating the degree of swelling according to the following formula from the length before and after swelling.
Swelling degree = {length after swelling} / {length before swelling}
The swelling degree of the synthetic polyisoprene crosslinked body with toluene is preferably 1.65 to 2.0, more preferably 1.70 to 1.95, and most preferably 1.73 to 1.90.

As a method for producing a synthetic polyisoprene crosslinked product having such characteristics, the following production method according to the second invention of the present invention and a synthetic polyisoprene crosslinked product obtained by the method were found.
That is, as described in claim 3,
Synthetic polyisoprene latex (S-0);
A composition comprising an organic peroxide having a one-minute half-life temperature of 100 ° C. to less than 120 ° C .;
The synthetic polyisoprene solid (S-1) from which the moisture of the composition was removed was
A synthetic polyisoprene crosslinked body (S-2) characterized by satisfying claim 1 or 2 by crosslinking at a crosslinking temperature of less than 120 ° C. and a method for producing the same.

Synthetic polyisoprene used as the main raw material is classified into four types of 1,4-cis adduct, 1,4-trans adduct, 3,4 adduct, and 1,2 adduct depending on the polymerization conditions, and is used in this patent. The synthetic polyisoprene latex (S-0) may have any of these structures, but polyisoprene mainly having a 1,4-cis polyisoprene structure composed of a 1,4-cis adduct is preferable. ,
Among those containing mainly a 1,4-cis adduct, there are those produced by an anionic polymerization method using a lithium catalyst and those produced by a coordination polymerization method using a Ziegler catalyst. Recently, there are a catalyst using a metallocene catalyst and a catalyst manufactured using a catalyst system using a rare earth, and industrially available catalysts include a lithium catalyst and a Ziegler catalyst.
Polymerization using a lithium catalyst contains about 92% of a 1,4-cis adduct, while polymerization using a Ziegler catalyst contains about 98% of a 1,4-cis adduct. In general, those produced using a Ziegler catalyst tend to contain a 1,4-cis adduct in a high ratio due to differences in reaction mechanism and the like compared to a lithium catalyst.
In stereoregularity, it is considered that the higher the ratio of 1,4-cis adduct, the higher the stereoregularity and the higher the crystallization. In the present invention, 80% equivalent or more of 1,4-cis structure is contained. It is essential to do.
From the viewpoint of stereoregularity, it is preferably 90 equivalent% or more, more preferably 92 equivalent% or more, and most preferably 92 equivalent% to less than 99 equivalent%. When the 1,4-cis structure is 80 equivalent% or less, the strength at break is not significantly improved, and the balance between the strength at break, elastic modulus and elongation is poor, which is not preferable.

Synthetic polyisoprene is available in the form of solid rubber or latex.
Examples of the solid rubber include those sold under the product name IR2200 manufactured by JSR Corporation, the product name Nipol IR2200 manufactured by Nippon Zeon Co., Ltd., and the product name Cariflex IR0307 manufactured by Kraton Polymer.
These synthetic polyisoprenes are known to contain 90% or more of 1,4-cis structures.
In addition, solid rubber can be emulsified and emulsified to be used as a synthetic polyisoprene latex (S-0).
On the other hand, what can be obtained as latex includes Sepolex IR-100K manufactured by Sumitomo Seika Co., Ltd., Cariflex IR0401 manufactured by Kraton Polymer Co., Ltd., Nipol ME series (developed product) manufactured by Nippon Zeon Co., Ltd. It is done.
These are known to contain 90% or more of the 1,4-cis structure.
In particular, among products available in Japan, IR-100K manufactured by Sumitomo Seika Co., Ltd. and IR0401 manufactured by Clayton Polymer Co., Ltd. are preferable. Most preferred is the use of IR-100K.
In addition, it is preferable to use synthetic polyisoprene in a latex state rather than a solid state because it does not take time for emulsification and can be used at a high concentration.
The application range of the synthetic polyisoprene solid (X) and the synthetic polyisoprene solid (X ′) in the present invention includes the synthetic polyisoprene crosslinked product (S-2).

The most characteristic of the production method in the synthetic polyisoprene crosslinked body is that the synthetic polyisoprene solid (S-) obtained by using the synthetic polyisoprene latex (S-0) and the peroxide having a relatively low half-life temperature. In 1), the crosslinked polyisoprene (S-2) is obtained by a crosslinking reaction at a relatively low temperature of less than 120 ° C. in the crosslinking step.
Synthetic polyisoprene obtained at a relatively low cross-linking temperature is surprisingly flexible. However, when the cross-linking temperature is 120 ° C. or higher, the polyisoprene is hardened too much and side reactions are likely to occur. Is unfavorable because it has a high elastic modulus, is hard and lacks flexibility, and there is a possibility that the main chain of the synthetic polyisoprene may be cleaved.
The temperature is not particularly limited as long as it is less than 120 ° C, but is preferably less than 50 to 120 ° C, more preferably 60 to 110 ° C, still more preferably 70 to 100 ° C, and most preferably 75 to 95 ° C. It is.
The crosslinking time is not particularly limited, but is preferably within 2 hours from the viewpoint of productivity.
However, a time that is 3 times or more of the half-life time is preferable, and a time that is 5 times or more and 10 times or less is more preferable.

It is essential that the 1 minute half-life temperature of the organic peroxide used in the present invention is 100 to less than 120 ° C.
When the half-life temperature for 1 minute is 120 ° C. or higher, as described above, the crosslinking temperature must be set high, and the finished product is hardened, the flexibility is lost, and the elastic modulus becomes higher than necessary. There is a fear.
Also, peroxides with a 1 minute half-life temperature of 120 ° C. or higher are not preferable if the crosslinking temperature is set low, which requires a long time for the crosslinking, resulting in very poor production efficiency.
Furthermore, when performing crosslinking in atmospheric water, which will be described later, it is necessary to use a pressurized state, which is not preferable because it is inefficient.
On the other hand, when the half-life temperature for 1 minute is less than 100 ° C., it decomposes near room temperature, the radical disappears, and there is a high risk of handling at room temperature, which is not preferable in terms of safety.
Among them, di (4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life 92.1 ° C.) (product name: Parroyl TCP, manufactured by NOF Corporation) can be stored near room temperature. Although it is a solid and relatively easy to handle, it is out of the scope of the present invention because of its weak hydrogen abstraction ability.

Therefore, as the organic peroxide used in the present invention,
t-Hexylperoxyneodecanoate (half-life 100.9 ° C. between 1), t-butylperoxyneodecanate (half-life 10 minutes at 13.5 ° C.), t-butylperoxyneodecanate (1 minute) Half-life 104.6 ° C.), t-hexyl peroxypivalate (1 minute half-life 109.1 ° C.), t-butyl peroxypivalate (1 minute half-life 110.3 ° C.), di (3,5,5 5-trimethylhexanol) peroxide (1 minute half-life 112.6 ° C), dilauroyl peroxide (1 minute half-life 116.4 ° C), 1,1,3,3-tetramethylbutylperoxy-2-ethyl Hexanate (1 minute half-life 124.3 ° C), disuccinic acid peroxide (1 minute half-life 131.8 ° C), 2,5-dimethyl-2,5-di (2-ethylhexene) Rupaokishi) hexane (1-minute half-life 118.8 ° C.) can be selected from.
These organic peroxides can be used alone or in combination.
Among them, dilauroyl peroxide is most preferable from the viewpoint of safety and hydrogen extraction capability because it can be stored at room temperature.

The half-life of the organic peroxide is an index representing the decomposition rate of the organic peroxide, and is indicated by the time required for the remaining amount of active oxygen from the original organic peroxide amount to half.
The 1-minute half-life temperature, the 1-hour half-life temperature, and the 10-hour half-life temperature specified in this patent are generally values described in “Organic peroxide catalog 10th edition” of NOF Corporation. When there is no description, as in the method described in the catalog, the value obtained from thermal decomposition in an organic solvent is used, and the concentration is 0.05 to 0.2 mol / L And

The concentration of the organic peroxide is preferably 0.1 to 2.0 equivalent% (mol%), more preferably 0.4 to 1.5 equivalent%, based on the number of double bond equivalents in the synthetic polyisoprene. More preferably, it is 0.5 to 1.3 equivalent%, and most preferably 0.6 to 1.3 equivalent%.
When the amount is less than 0.1 equivalent%, the crosslinking reaction is not sufficiently performed, and therefore the strength is very weak, which is not preferable.
When the amount exceeds 2.0 equivalent%, the crosslinking reaction proceeds excessively, becomes too hard, and the elongation and strength decrease, which is not preferable.

The organic peroxide used in the present invention is hydrophobic, and when mixed with a synthetic polyisoprene latex, an anionic or nonionic surfactant is added after dissolving the organic peroxide in an organic solvent. If necessary, it can be used as a peroxide slurry that is added with water, stirred at high speed, and slurried (emulsified). Thereafter, it is put into the synthetic polyisoprene latex (S-0), stirred for a predetermined time, and then solidified with a drying process or a coagulating liquid to obtain an uncrosslinked synthetic polyisoprene solid (S-1). .
In other methods, the slurry of organic peroxide (emulsification) is preferably performed by the method described in JP-A-59-68303, because a peroxide slurry can be produced without using an organic solvent.
In addition, when using a crosslinking agent described later in combination with an organic peroxide, a method in which the peroxide slurry and the synthetic polyisoprene latex are mixed and then the crosslinking agent is added, or the stability of the emulsion is unstable. In this case, a method of adding a crosslinking agent after adding a surfactant can be used.
Further, a crosslinking agent may be added when the peroxide slurry is produced.

The stirring time for mixing the organic peroxide emulsion or the crosslinking agent with the synthetic polyisoprene latex (S-0) is preferably less than 1 hour, more preferably less than 30 minutes.
When the stirring time is 1 hour or more, the stability of the latex is deteriorated and the viscosity may be increased, and radicals in the latex may be deactivated.
After the stirring, solidification is performed using a coagulating liquid such as a drying process or a calcium nitrate liquid without going through an aging process.
Since the aging step is not required, it is possible to obtain a crosslinked body in which radical deactivation is kept to a minimum, the effective radicals are constant, and the degree of crosslinking is stable.

By adding a specific cross-linking agent in combination with an organic peroxide, the mechanical properties are improved.
The cross-linking agent is a polyfunctional methacrylate, for example, ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, neo Pentyl glycol dimethacrylate, ethoxylated bisphenol dimethacrylate, trimethylolpropane trimethacrylate, etc.
Polyfunctional acrylates include ethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,10-decanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, Examples thereof include tetraethylene glycol diacrylate and trimethylolpropane triacrylate.
These compounds can be obtained from Sakai Kogyo Co., Ltd., Shin-Nakamura Chemical Co., Ltd., NOF Corporation, Kyoeisha Chemical Co., Ltd., Mitsubishi Rayon Co., Ltd., etc.
Among these crosslinking agents, from the viewpoint of reactivity, the methacrylate type is preferable because the reaction occurs milder than the acrylate type.
More preferably, it is a bifunctional methacrylate. In addition, since the double bond which exists in these crosslinking agents is equivalent, the reactivity is the same.
Among these cross-linking agents, 1,4-butanediol dimethacrylate, ethylene glycol dimethacrylate, and 1,6-hexanediol dimethacrylate are preferred, and ethylene glycol dimethacrylate is characterized by good stability when mixed with latex. 1,6-hexanediol dimethacrylate is preferred because it is easy to mix with synthetic polyisoprene latex.

On the other hand, natural products such as limonene and pinene, 1,6-octadiene, ethylidene norbornene and the like have double bond groups (reactive groups) with different non-equivalent reactivities, so the reaction may be controlled. In some cases, functional groups that are difficult to react may remain unreacted, which is not preferable.
Moreover, when the reactivity is equivalent, since two reactive groups are easy to react together, it is easy to bridge | crosslink and it is preferable.
When a crosslinking agent having three or more functional groups is used, the strength is greatly improved, but the elastic modulus tends to increase with it, and the flexibility is poor, which is not preferable.
In addition, a compound having a polyfunctional vinyl group, a compound having a polyfunctional thiol group, and the like can be used. However, when a crosslinking agent having a thiol group is used, the sulfur content is within the range of claim 1. is necessary.

On the other hand, a monofunctional silane coupling agent can also be used as a crosslinking agent.
This is because in the case of a silane coupling agent, a silanol group can be condensed to become a polyfunctional group.
Another advantage is that the silane contained in the silane coupling agent exhibits the effect of reducing surface tack.

A preferable silane coupling agent is a silane coupling agent having a double bond or a thiol group.
Examples of the silane coupling agent having a double bond include (1) vinyl silane, (2) methacryl silane, (3) acrylic silane, and (4) styryl silane.
(1) Examples of vinyl silane include vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tris (2-methoxyethoxy) silane vinyl methyl dimethoxy silane, and mixtures thereof.
(2) Examples of methacrylsilane include 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane.
(3) Examples of acrylic silane include 3-acryloxypropyltrimethoxysilane.
(4) Examples of styrylsilane include p-styryltrimethoxysilane.
Among (1) to (4), (1) vinylsilane and (2) methacrylsilane are preferable from the viewpoint of reactivity.
Of these, vinyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane are preferable, and vinyltrimethoxysilane is most preferable from the viewpoint of reactivity and price.
On the other hand, examples of the silane coupling agent having a thiol group include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and the like.
Of these, 3-mercaptopropyltrimethoxysilane is most preferred in terms of price and reactivity.

These crosslinking agents can be used singly or in combination, and can be controlled using several kinds.
In addition, excellent mechanical properties can be realized without blending these crosslinking agents, but when blending a crosslinking agent, the elastic modulus is lower and the breaking strength is improved, breaking strength, elongation. The balance between the modulus and elastic modulus is further improved.
The blending amount of the crosslinking agent is essentially a concentration of 0 to 15 equivalent% in terms of the ratio (equivalent%) of the number of functional groups of the crosslinking agent and the number of double bond equivalents of polyisoprene, preferably 0.5 to 10 equivalents. %, More preferably 1.0 to 8 equivalent%, still more preferably 2.0 to 7.0 equivalent%, and most preferably 3.0 to 6.0 equivalent%.

The drying temperature for drying the synthetic polyisoprene latex mixed with the peroxide slurry to obtain an uncrosslinked synthetic polyisoprene solid (S-1) is preferably relatively low, and is a temperature of 60 ° C. or lower. It is preferable to carry out at 20 degreeC to 50 degreeC more preferably.
If it exceeds 60 ° C., the surface becomes sticky, which is not preferable.
In addition, you may add antioxidant as needed. Although it does not specifically limit as antioxidant, It is a non-fouling antioxidant, and especially phenolic antioxidant is preferable.
In addition to the drying step, a step of immersing the peroxide slurry mixed latex in the coagulating liquid and coagulating it may be selected.
The coagulation liquid is obtained by dissolving a calcium salt (calcium nitrate, calcium chloride, calcium acetate, etc.) in a solvent (hydrophilic solvent such as water, alcohol, ketone, etc.).
In addition, a drying process can also be abbreviate | omitted when the process immersed in this coagulating liquid is used, or when the bridge | crosslinking process mentioned later is performed in a drying furnace.
The uncrosslinked synthetic polyisoprene solid (S-1) obtained by the drying process or the coagulation process obtains a synthetic polyisoprene crosslinked body (S-2) by a crosslinking process described later.

Generally, in the peroxide crosslinking of synthetic polyisoprene, the stickiness of the surface layer that occurs in parallel with the crosslinking reaction significantly reduces the product performance. That is, when the cross-linking reaction is performed in the presence of oxygen, the main chain is broken by oxidation, resulting in stickiness on the surface, and the elongation rate tends to decrease due to the main chain cleavage.
For this reason, surface stickiness and a decrease in elongation rate can be prevented by avoiding contact with oxygen during the crosslinking reaction.
Therefore, it must be carried out in a substantially oxygen-free state under the atmosphere in the crosslinking reaction.
That is, when the crosslinking reaction is performed in an oxygen-free state or an atmosphere with as little oxygen as possible, specific methods include (A) vacuum crosslinking, (B) inert gas crosslinking performed in an inert gas atmosphere, (C ) Warm water cross-linking performed in a liquid with low dissolved oxygen (mainly in water).

(A) As vacuum crosslinking,
A method of vacuuming the inside of the heating furnace and degassing oxygen, putting it in a container covering uncrosslinked synthetic polyisoprene solid (S-1) or a bag that can be hermetically sealed, vacuuming, and evacuating the container Thus, a method of heating from the outside of the container can be used.
However, in order to evacuate the inside of the heating furnace, it is necessary to perform suction under reduced pressure, and the heating furnace needs to be pressure resistant.

(B) As inert gas crosslinking,
The inert gas can be selected from nitrogen gas, argon gas, helium gas, etc., but nitrogen gas is preferable from the viewpoint of ease of handling and price.
As a crosslinking method under an inert gas atmosphere, a method of replacing the entire heating furnace with an inert gas, a container covering an uncrosslinked synthetic polyisoprene solid (S-1) or a bag that can be hermetically sealed, A method of replacing the inert gas and heating from the outside of the container can be used.

(C) Hot water cross-linking requires removal of dissolved oxygen in water, and as a method of removing dissolved oxygen, a method of performing pressure replacement with an inert gas, a method of performing pressure reduction replacement with an inert gas, an inert gas There are a bubbling method and a combination method thereof, and the most effective deoxygenation is the reduced pressure replacement, but any one of the replacement methods of normal pressure, increased pressure and reduced pressure can be selected.
When the inert gas replacement is performed, it is preferably performed in a closed system that blocks external oxygen. For example, an apparatus such as an autoclave can be used. However, when the container is not a closed system, bubbling with an inert gas is performed. For example, a method of removing dissolved oxygen out of the system is used.
In this case, since the apparatus does not need to have a pressure resistance specification, the bubbling method using an inert gas is most preferable in that it can be made inexpensive.
In the cross-linking step after the inert gas replacement, this method is preferable in that the cross-linking reaction can be performed under normal pressure.
In the case of a heating temperature of 100 ° C. or lower, the water does not become pressurized even when heated to a predetermined temperature, but when the heating temperature is higher than 100 ° C. to lower than 120 ° C., a salt such as sodium chloride is added. It is possible to carry out under normal pressure by dissolving in water and utilizing the rise in boiling point.

The amount of dissolved oxygen in water is preferably less than 4 ppm in water.
The amount of dissolved oxygen is less than 4 ppm, more preferably less than 3 ppm, and most preferably less than 1 ppm.
If the amount of dissolved oxygen is 4 ppm or more, the surface becomes sticky, which is not preferable.
The water used here is not particularly limited, but can be selected from distilled water, purified water, ion-exchanged water, tap water, and the like.

In particular, warm water crosslinking can be performed also as leaching, and therefore is a most preferable method in the crosslinking method in (A) to (C) because the process is shortened and can be manufactured with a simple apparatus. .
Further, by performing the leaching, unnecessary components such as a surfactant are removed, so that there is an effect that a significant improvement in strength is expected.
After the hot water crosslinking, moisture on the solid is removed by a drying process.
The drying temperature is not particularly specified, but it is preferably performed at a temperature lower than 120 ° C, more preferably from room temperature to 80 ° C.
The crosslinking methods (A) to (C) in the above can be selected by a single method or a combined method.

The synthetic polyisoprene crosslinked product described above can be manufactured using conventional molding equipment. Examples of molding methods include immersion (dipping) molding and casting molding. Preferably, it is performed by immersion molding.
In the case of making an immersion product, an immersion molded product can be obtained by a conventionally known method described in “Emulsion Latex Handbook” or the like.
The synthetic polyisoprene cross-linked product obtained by the present invention is a material having high breaking strength, excellent flexibility, and high elongation rate, and is a low-toxic composition that solves allergic problems and N-nitrosamine problems. Especially suitable for medical and hygiene materials, mainly suitable for gloves, balloons, finger sack, condoms, catheters, injection needle plugs, and because of its high elongation rate and flexibility, gloves, balloons, catheters Most suitable for
Other products that come into direct contact with human skin and organs are very useful because of their low toxicity and non-toxicity.
Furthermore, it can be used in industrial applications, particularly in the fields of electronic materials, medical applications, cosmetics, construction fields, shape memory gels, soft actuators such as artificial muscles, and other fields that require high-performance materials.

These can be produced simply and at low cost by the method described in claims 4 to 12.
When a small amount of an antioxidant, a UV absorber, or the like is added as an additive of the synthetic polyisoprene latex, it may be used as long as it does not contradict the gist of the present invention.
Further, in addition to the main component synthetic polyisoprene latex, even if a small amount of SBR, NBR or other latex is added in a small amount, it may be used as long as it does not violate the gist and claims.
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

The evaluation method in a present Example and a comparative example is demonstrated below.
(1) Fluorescent X-ray measurement of sulfur element JSX-3200 manufactured by JEOL Ltd. was used as the fluorescent X-ray apparatus.
A sheet of solid polyisoprene with a thickness of about 1 mm is prepared, and the intensity of the elements constituting the sample is read from the intensity of the fluorescent X-ray, and the relationship between the intensity and the content is determined using a standard sample or a specified amount. A sheet with the sample added was prepared, and a calibration curve was prepared and obtained.
Some of them were also measured by ICP, and the values obtained by fluorescent X-rays and the values obtained by ICP showed very good agreement.
(2) Mechanical properties The mechanical properties were measured using Autograph AGS-1 kgNG manufactured by Shimadzu Corporation.
A sheet of a synthetic polyisoprene crosslinked product (X, X ′ and S-2) having a thickness of about 1 mm was prepared, and a test piece was obtained using a No. 4 dumbbell. Measured by a tensile test method at a speed of 500 mm / min, and values of 300% elastic modulus, 500% elastic modulus, and 700% elastic modulus were adopted for elongation to break, strength at break, and elastic modulus, respectively. .
(3) Swelling degree A sheet of a specific size is cut out from the sheet at the time of measuring the mechanical properties, immersed in toluene for 24 hours at room temperature, the swollen length is measured, and the degree of swelling is obtained from the length before and after that. It was.
(4) Amount of dissolved oxygen The amount of dissolved oxygen was measured using a portable dissolved oxygen meter HORIBA DOMETER OM-70 manufactured by HORIBA, Ltd.
(5) Surface texture The surface texture was determined by a sensory evaluation based on a human hand feeling of the stickiness on the rubber sheet surface.
Evaluate the feel when five people touch the rubber sheet surface with their hands,
The five people all judged to be non-sticky are indicated by “◎”
“○” indicates that one or more of the 5 people evaluated that surface tack remains.
“△” means that one or more of the five people evaluated it as somewhat sticky.
What all five people evaluated to be clearly sticky was rated as “x”.

Examples will be described below.
Tables 1 and 2 describe various performances in the examples, and Table 3 lists various performances in the comparative examples.
Moreover, the physical property value of the synthetic polyisoprene solid sheet | seat of Sumitomo Seika Co., Ltd. product Sepolex IR-100K used as a main raw material was described in Table 3 as a reference example.

<Preparation of organic peroxide slurry>
(I) Various organic peroxides: 20.2 g was taken in a beaker and dissolved in chloroform: 80 g. After confirming complete dissolution, a surfactant was added and then diluted with water to obtain a peroxide slurry.
In addition, the addition amount of water was adjusted so that it might become 10.7% as solid content concentration of a peroxide.
(II) A slurry of dilauroyl peroxide was prepared by a method according to a patent (Japanese Patent Laid-Open No. Sho 59-68303) of NOF Corporation.

<Crosslinking device>
(A) Vacuum cross-linking apparatus A vacuum constant temperature dryer VOS-201SD manufactured by Tokyo Rika Kikai Co., Ltd. was used.
(B) Inert gas bridge | crosslinking apparatus Inert gas substitution was performed using nitrogen gas using the vacuum constant temperature dryer VOS-201SD by Tokyo Rika Kikai Co., Ltd. company.
(C) Hot water bridging apparatus Stainless steel sealable container, having a pipe for introducing and bubbling nitrogen and a pipe for venting the gas in the container, and a function of heating the inside of the container was provided. A hot water crosslinking apparatus was used.

Example 1
Synthetic polyisoprene latex (S-0), Sepolex IR-100K manufactured by Sumitomo Seika Co., Ltd .: 150 g and dilauroyl peroxide (1 minute half-life temperature 116.4 ° C.) 48.6 g of the peroxide slurry prepared by the method (I) using the product name of “Perroyl L”, and then 6.5 g of 1,6-hexanedimethacrylate as a cross-linking agent were added. The mixture was kept at a temperature of 25 ° C., stirred for 15 minutes, and allowed to stand.
The obtained peroxide-containing polyisoprene latex is poured onto a glass plate and left on a hot plate heated to about 40 ° C. for 24 hours to evaporate water and to give an uncrosslinked polyisoprene solid having a thickness of about 1 mm. (S-1) A sheet was obtained.
As shown in Table 1, the compounding ratio (the ratio of the peroxide and the crosslinking agent to the synthetic polyisoprene) in the synthetic polyisoprene solid (S-1) sheet is as follows.
[Peroxide (number of moles) / [number of double bonds (number of equivalents)] × 100 = 0.91 (equivalent% ratio), [crosslinking agent (number of moles)] / [number of double bonds (number of equivalents) ] × 100 = 1.79 (equivalent% ratio), so [number of functional groups (number of equivalents)] / [number of double bonds (number of equivalents)] × 100 = 3.58 (equivalent% ratio) .
The obtained uncrosslinked synthetic polyisoprene solid (S-1) sheet was placed in a hot water crosslinking apparatus of the crosslinking apparatus (C), tap water was added, and the solid sheet was added to a height that sufficiently immerses the solid sheet.
Next, bubbling with nitrogen gas was performed for 15 minutes at room temperature, and oxygen in the water in the container was removed by bubbling.
The oxygen concentration in the water before bubbling nitrogen was 6 ppm.
The oxygen concentration in the water after bubbling nitrogen was less than 1 ppm.
Thereafter, the inside of the container was heated, the water temperature was rapidly increased, and when the temperature reached 87 ° C., a crosslinking reaction was performed for 2 hours.
After 2 hours, rapid cooling was performed, and after cooling to about 50 ° C., the sheet was taken out of the water and washed.
Nitrogen bubbling was continued until the sheet was removed.
In order to remove the moisture on the sheet, it was dried at 60 ° C. for 30 minutes with a dryer, and the No. 4 dumbbell and the sample for swelling test were cut out from the obtained synthetic polyisoprene (S-2) solid sheet after crosslinking, and mechanical properties And a swelling test.
The physical property values and evaluation results of the synthetic polyisoprene (S-2) are shown in Table 1.
In the evaluation of the surface property, since all of the five people evaluated that there was no stickiness, it was determined as “◎”.

(Example 2)
The same procedure as in Example 1 was performed except that the concentration of the peroxide and the crosslinking agent, the crosslinking temperature and the crosslinking time were changed.

(Example 3)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to ethylene glycol dimethacrylate.

Example 4
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to ethylene glycol dimethacrylate and the crosslinking temperature and time were changed.

(Example 5)
The manufacturing method of the peroxide slurry was changed to the method (II), and the same procedure as in Example 1 was performed except that the concentrations of the peroxide and the crosslinking agent were changed.

(Example 6)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to trimethylolpropane trimethacrylate and the concentrations of the peroxide and the crosslinking agent were changed.

(Example 7)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to vinyltrimethoxysilane.

(Example 8)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to 3-mercaptopropyltrimethoxysilane and the concentrations of the peroxide and the crosslinking agent were changed.

Example 9
The same procedure as in Example 1 was performed, except that no crosslinking agent was added and the peroxide concentration was changed.

(Example 10)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to ethylene glycol dimethacrylate and the concentrations of the peroxide and the crosslinking agent were changed.

(Example 11)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to ethylene glycol dimethacrylate and the crosslinking temperature and the crosslinking time were changed.

(Example 12)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to neopentyl glycol dimethacrylate.

(Example 13)
The same method as in Example 1 except that the cross-linking agent was changed to ethylene glycol dimethacrylate, the cross-linking temperature was changed to 110 ° C. using saline instead of tap water used in the hot water cross-linking apparatus, and the cross-linking time was changed. I went there.

(Example 14)
Nitrogen bubbling at the time of replacing the nitrogen gas with the hot water crosslinking apparatus was stopped when the dissolved oxygen amount reached 1.5 ppm, and the crosslinking was performed in the state of the dissolved oxygen amount, and the same method as in Example 1 was performed. It was.
In the evaluation of the surface property, 3 persons out of 5 evaluated that surface tack remained, and 2 persons evaluated that there was no stickiness.

(Example 15)
Nitrogen bubbling at the time of replacing nitrogen gas with a hot water crosslinking apparatus was stopped when the dissolved oxygen content reached 3.5 ppm, and was performed in the same manner as in Example 1 except that crosslinking was performed in the state of the dissolved oxygen content. It was.
In the evaluation of the surface property, 4 out of 5 people evaluated that the surface was slightly sticky, and 1 person evaluated that the surface tack remained.

(Example 16)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to ethylene glycol dimethacrylate and crosslinking was performed under vacuum using a vacuum crosslinking apparatus of the crosslinking apparatus (A).
In addition, when the amount of oxygen in the apparatus was measured, the amount of oxygen was less than 1 ppm. The oxygen amount was measured using an oxygen concentration meter XP-3180 manufactured by Shin Cosmos Electric Co., Ltd.

(Example 17)
Except for changing the cross-linking agent to ethylene glycol dimethacrylate, changing the concentration of peroxide and cross-linking agent, cross-linking temperature and cross-linking time, and performing cross-linking with the inert gas cross-linking device of the cross-linking device (B). The same method as in Example 1 was used.
In addition, when the amount of oxygen in the apparatus was measured by the same measurement method as in Example 16, the amount of oxygen was less than 1 ppm.

(Example 18)
The same procedure as in Example 1 was performed except that the crosslinking was performed by the inert gas crosslinking device of the crosslinking device (B).
In addition, the amount of oxygen in the apparatus was measured by the same measurement method as in Example 16, and crosslinking was performed when the amount of oxygen reached 2.5 ppm.
In the evaluation of the surface property, 3 persons out of 5 evaluated that surface tack remained, and 2 persons evaluated that there was no stickiness.

(Example 19)
In order to perform immersion processing using a finger sack mold, the finger sack mold is immersed in a mixture of peroxide slurry and synthetic polyisoprene latex. The film was immersed in a coagulation liquid to obtain a film having a thickness of about 0.3 mm.
Next, crosslinking was performed with a hot water crosslinking apparatus of the crosslinking apparatus (C), and the obtained crosslinked film was removed from the mold and dried with a dryer at 70 ° C. for 10 minutes to obtain a finger sack molded product.
In addition, the compounding ratio and the compounding method of the peroxide and the like, and the crosslinking conditions were the same as in Example 1.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the peroxide was changed to the product name “Nyper BW” of NOF Corporation, which is dibenzoyl peroxide (1 minute half-life temperature 130.0 ° C.). .

(Comparative Example 2)
Except for changing the peroxide to NOF Corporation's product name "Parroyl TCP" which is di (4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life temperature 92.1 ° C) The same method as in Example 1 was used.

(Comparative Example 3)
As a redox catalyst, Wako Pure Chemical Industries, Ltd. tetraethylenepentamine (TEPA) as a reducing agent, and peroxide is t-butyl hydroperoxide (1 minute half-life temperature 260.7 ° C.) NOF A product name “Perbutyl H-69” manufactured by Co., Ltd. was used for the reaction without using a crosslinking agent.
In addition, the peroxide slurry and the synthetic polyisoprene latex prepared without using chloroform by the method (I) were mixed, and then the reducing agent was mixed to obtain a composition of the peroxide and the synthetic polyisoprene latex. .
The same procedure as in Example 1 was performed except that the peroxide concentration, the crosslinking temperature and the crosslinking time were changed.

(Comparative Example 4)
The same procedure as in Example 1 was performed except that the peroxide was changed to the product name “Park Mill D” of NOF Corporation, which is dicumyl peroxide (1 minute half-life temperature 175.2 ° C.).

(Comparative Example 5)
The same procedure as in Example 1 was performed except that the crosslinking temperature and the crosslinking time were changed.

(Comparative Example 6)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to ethylene glycol dimethacrylate and the concentrations of the peroxide and the crosslinking agent were changed.

(Comparative Example 7)
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to glycerin triacrylate.

(Comparative Example 8)
The same procedure as in Example 1 was performed except that the crosslinking apparatus (C) was used for crosslinking in a state where the dissolved oxygen content was 6 ppm without nitrogen bubbling.
In the evaluation of the surface properties, since all of the 5 people evaluated that they were clearly sticky, they were judged as “x”.

(Comparative Example 9)
The same procedure as in Example 1 was performed except that the crosslinking apparatus (A) was used for crosslinking under hot air.
In the evaluation of the surface properties, since all of the 5 people evaluated that they were clearly sticky, they were judged as “x”.

Claims (14)

The composition comprising the synthetic polyisoprene latex (S-0) is solidified and cross-linked, and is a synthetic polyisoprene cross-linked product (X).
The strength at break (TS) is 15 MPa or more,
And satisfy | fills at least 2 among following numerical formula (1)-(3),
Synthetic polyisoprene crosslinked product (X) characterized in that the amount of sulfur element is 500 ppm or less

The synthetic polyisoprene crosslinked product (X ') according to claim 1, which satisfies all of the following formulas (4) to (6):

Synthetic polyisoprene latex (S-0);
A composition comprising an organic peroxide having a one-minute half-life temperature of 100 ° C. to less than 120 ° C .;
The synthetic polyisoprene solid (S-1) from which the moisture of the composition was removed was
Synthetic polyisoprene crosslinked product (S-2) characterized by satisfying claim 1 or 2 by performing crosslinking at a crosslinking temperature of less than 120 ° C. The manufacturing method of the synthetic polyisoprene crosslinked body (S-2) of Claim 3 The said peroxide is a dilauroyl peroxide, The manufacturing method of the synthetic polyisoprene crosslinked body (S-2) of Claim 4 characterized by the above-mentioned. 6. The synthetic polyisoprene solid product (S-2) according to claim 4 or 5, wherein the synthetic polyisoprene solid (S-1) is crosslinked in a substantially oxygen-free state. Method In the crosslinking step of the synthetic polyisoprene solid (S-1),
In water with less than 4 ppm of dissolved oxygen,
The method for producing a crosslinked synthetic polyisoprene (S-2) according to any one of claims 4 to 6, wherein the synthetic polyisoprene solid (S-1) is immersed at a temperature of less than 120 ° C. The method for producing a crosslinked synthetic polyisoprene (S-2) according to claim 6 or 7, wherein the dissolved oxygen in the water is replaced with an inert gas. The process for producing a synthetic polyisoprene crosslinked product (S-2) according to any one of claims 6 to 8, which is carried out under normal pressure. In a composition containing a synthetic polyisoprene latex (S-0) and an organic peroxide,
A method for producing a crosslinked synthetic polyisoprene (S-2) according to any one of claims 4 to 9, comprising a crosslinking agent. The method for producing a synthetic polyisoprene crosslinked product (S-2) according to claim 10, wherein the crosslinking agent is a polyfunctional (meth) acrylate. The method for producing a crosslinked polyisoprene (S-2) according to claim 10, wherein the crosslinking agent is a silane coupling agent having a double bond or a thiol group. Synthetic polyisoprene crosslinked bodies (X) and (X ′) according to claim 1 and 2 and medical and hygiene products including an immersion product using the synthetic polyisoprene crosslinked body (S-2) according to claim 3. Rubber product A rubber product for medical and hygiene comprising an immersion product produced by the method according to claims 4-12.