JPH0330418B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hydrosol composition whose physical properties are significantly improved by intraparticle crosslinking, and a method for producing the same. Conventionally, in order to obtain hydrosol, for example,
As seen in JP-A-22343 and JP-A-19842, polymer particles containing carboxyl groups and having a particle diameter of about 0.3 to 0.7 μm obtained by emulsion polymerization are treated in the presence of an alkali. By stirring at high speed, the particle surface is gradually scraped off, reducing the particle size to approx.
A so-called strippable method, which produces fine particles of 0.01 to 0.1 μm, has generally been adopted. However, with the above method, the emulsifier used during polymerization remains in the resulting hydrosol particles, resulting in poor water resistance of coatings and other molded products, and also limits the molecular weight of the polymer that can be converted into a hydrosol. Generally, when the weight average molecular weight is 10 ⁴ or more, it becomes difficult to form a hydrosol. Therefore, there are natural limitations in terms of compatibility with various uses,
Applications had only been developed mainly in the paint field and paper size field. Therefore, the present inventors synthesized a copolymer having acidic groups in the molecule in a specific ratio in JP-A-58-136647, and added alkali and water to it to remove some or all of the acidic groups. We proposed a method to obtain hydrosol by neutralizing and inverting the phase. Since the hydrosol obtained by this method does not contain an emulsifier in the particles, it has very good water resistance when used as a coating or other molded product, and it also allows the molecular weight of the copolymer to be relatively large. Therefore, various physical properties are also improved. Therefore, it has the advantage that it can be applied not only to paints and paper sizing agents, but also to a wide range of applications such as adhesives, adhesives, overcoating agents, exterior materials, interior materials, packaging materials, and films. On the other hand, depending on the application, for example, in applications such as vacuum adhesives, it is necessary to increase the cohesive force, and in this case, a crosslinking agent is added to the hydrosol composition to cause a crosslinking reaction after molding. Because the continuous phase of the hydrosol is water, the crosslinking agent used is limited to water-soluble or water-dispersible types. With crosslinking using such crosslinking agents, it is difficult to uniformly disperse the inside of the hydrosol, which has relatively high hydrophobicity, and the crosslinking reaction mainly proceeds on the surface of the hydrosol particles, making it impossible to obtain hydrosol particles with excellent internal cohesive force. There is a problem in that a proper crosslinking reaction is not carried out, and the above method has not yet been fully satisfactory. In view of the above-mentioned problems, the present invention was discovered as a result of various studies to obtain a hydrosol composition with excellent separation properties. % and 80 to 98% by weight of an acrylic unsaturated monomer copolymerizable with the copolymer with a weight average molecular weight of ¹⁰⁴ to ¹⁰⁶ ,
It has the form of water-dispersed hydrosol particles with an average particle diameter of 0.01 to 0.1 μm that are neutralized in the presence of alkali and water and phase inverted to O/W type, and the hydrosol particles contain ethylenically unsaturated bonds. Another embodiment relates to a hydrosol composition characterized in that it is cross-linked by monomers having two or more of the following: 2 to 20% by weight of unsaturated monomers having acidic groups.
and an acrylic unsaturated monomer that can be copolymerized with it.
A first step of polymerizing a monomer mixture consisting of 80 to 98% by weight to obtain a copolymer, and adding an alkali and water to the copolymer to neutralize or convert some or all of the acidic groups. Combined, average particle size 0.01~0.1μm
A second step of obtaining a hydrosol that is stably dispersed in water, and based on 100 parts by weight of the solid content of the hydrosol.
A hydrosol composition comprising a third step of adding 0.01 to 15 parts by weight of a monomer having two or more ethylenically unsaturated bonds and impregnating it into the hydrosol particles, and then performing a cross-linking reaction. This relates to a manufacturing method. In the hydrosol composition of the present invention, a copolymer of a specific monomer in a specific amount is made into a hydrosol with a fine particle size, and then a monomer having cross-linking properties is impregnated inside the hydrosol particles and then weighted. As a result, the particle interior of the composition is uniform and highly three-dimensional, and properties such as adhesive properties and cohesive force when used as a pressure-sensitive adhesive, for example, are significantly improved. Therefore, unlike conventional methods, it is not necessary to add an external crosslinking agent, and high-temperature heat treatment during or after molding is not necessary, so that a low-energy, low-cost composition can be obtained. Moreover, since no special heat treatment is required,
It can prevent non-uniform crosslinking and changes in physical properties over time due to residual crosslinking agent, and also contributes to improved productivity such as increased coating speed. In order to obtain a hydrosol composition with the above characteristics, the first step is to prepare a copolymer consisting of an unsaturated monomer having an acidic group and another acrylic unsaturated monomer that can be copolymerized with this monomer. As the former monomer, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, styrene sulfonic acid, allyl sulfonic acid, sulfopropyl acrylate, 2 -Acryloyloxynaphthalene-2
-sulfonic acid, 2-metharyloyloxynaphthalene-2-sulfonic acid, 2-acrylamide-2-
Examples include unsaturated sulfonic acids such as methylprapanesulfonic acid and 2-acroyloxybenzenesulfonic acid, and examples of the latter monomer include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate,
Examples include (meth)acrylic acid alkyl esters in which the alkyl group has 2 to 15 carbon atoms, such as ethyl methacrylate and butyl methacrylate. Furthermore, as a modifying monomer, (meth)acrylic acid alkyl esters in which the number of carbon atoms in the alkyl group is outside the above range, such as methyl acrylate and methyl methacrylate, vinyl acetate, acrylonitrile, styrene, and acrylic acid 2 are used.
-methoxyethyl, vinyl ethers, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, acrylamide,
It is also possible to substitute and use a monomer such as N-methylol acrylamide in an amount of 40% by weight or less of the above monomer. The proportion of the unsaturated monomer having an acidic group and other acrylic unsaturated monomers copolymerizable with it is 2 to 20% by weight for the former and 80 to 98% by weight for the latter. Preferably, the former should be 3 to 10% by weight, and the latter should be 90 to 97% by weight. If the amount of the former monomer used is less than 2% by weight, it will be difficult to form a hydrosol in the second step, and if it is used in excess of 20% by weight, tackiness, adhesion, and other physical properties may deteriorate. This is not desirable as it may cause deterioration. A mixture of these monomers can be copolymerized by conventionally known methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. This is a solution polymerization method using a solvent. Among these polymerization methods, in the bulk polymerization method, the acrylic polymer obtained by the polymerization method can be used as it is as a raw material for hydrosolization. In the solution polymerization method, if the amount of solvent used is more than 20% by weight, the organic solvent is removed after polymerization by means such as distillation, but even if the amount is less than 20% by weight, the content is reduced or eliminated by the above methods. It is desirable to do so. As the solvent used in this solution polymerization method, various general organic solvents can be used, but methyl alcohol, ethylene alcohol, n-
It is desirable to use alcohol-based hydrophilic solvents such as butyl alcohol, n-propyl alcohol, isopropyl alcohol, and sec-butyl alcohol, or oligomers or prepolymers having hydrophilic groups such as hydroxyl groups, carboxyl groups, and amino groups. On the other hand, in other polymerization methods, the medium used in each method is removed by appropriate means after synthesis to obtain a solid material substantially free of medium. That is, in the emulsion polymerization method, water is removed by coagulating and separating by salting out, and in the suspension polymerization method, water is removed by filtering the particulate copolymer. At this time, it is desirable that the medium other than the organic solvent be completely removed, but some remaining is allowed. In addition, in the emulsion polymerization method and suspension polymerization method, some of the emulsifier or dispersant used during polymerization adheres to the surface of the copolymer particles, but these are removed during the above-mentioned medium removal operation, and if necessary, It can be almost completely removed by washing several times. In addition, in the emulsion polymerization method, highly three-dimensional copolymers, so-called gelled products, may be produced, but such copolymers may interfere with hydrosolization in the second step. Therefore, it is desirable to prevent the formation of the copolymer as much as possible during emulsion polymerization. However, even if a small amount of the copolymer is produced, it can be solved by masticating using a mixing roll, a Banbury mixer, etc., and applying a high shearing force. It is necessary to design the weight average molecular weight of the copolymer obtained in this way to be in the range of 10 ⁴ to 10 ⁶ ; if the molecular weight is too low, the cohesive strength will be poor when used as a molded product, such as a pressure-sensitive adhesive tape. If the molecular weight is too high, it will be difficult to form a hydrosol in the second step, and the adhesive force will decrease in terms of physical properties, which is not preferable. In the second step, while stirring the copolymer obtained as above, alkali and water are added to neutralize some or all of the acidic groups in the copolymer, and to form an O/W type. A water-dispersed hydrosol is prepared by phase inversion of
After adding 20 parts by weight or less of an alcoholic water-soluble solvent such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, or sec-butyl alcohol, an alkali and water may be added for phase inversion. Examples of the alkali used here include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, amines such as ethylamine and propylamine, ammonia, and α-aminoethyl alcohol. After hydrosolization, for example, it is desirable to use a volatile material that can be easily dispersed when it is coated on a tape support and dried, and it is preferable to use a volatile material that can be easily scattered when it is coated on a tape support and dried. etc. can be prevented. The amount of the alkali to be used may be about 0.02 to 2 equivalents relative to the acidic groups of the copolymer in order to neutralize some or all of the acidic groups. The temperature during neutralization treatment can be appropriately set depending on the type and properties of the copolymer, but is generally preferably in the range of 30 to 95°C. An example of the method for neutralization treatment and hydrosolization is to add a predetermined amount of alkali or alkaline solution to the copolymer polymerized and separated in the first step, stir and mix thoroughly, and then gradually add water. In addition, by phase inversion, water is made into a continuous phase, and copolymer particles are finely dispersed in O/W.
There is a method of producing a type of dispersion, but the method is not limited to this in any way, and an aqueous alkaline solution may be added instead of the water used during phase inversion, and neutralization treatment and hydrosolization may be performed simultaneously. The water-dispersed hydrosol thus obtained is
It is stably dispersed with an average particle size in the range of 0.01 to 0.1 μm, and its viscosity is preferably 0.1 to 1000 poise at a solid content concentration of 5 to 45% by weight and a measurement temperature of 25°C. Adding a monomer having two or more ethylenically unsaturated bonds to the hydrosol obtained in the second step,
The third step of impregnation and intraparticle polymerization is a particularly important step for exhibiting the characteristics of the hydrosol composition of the present invention, and the monomer is poly(meth)acrylate of polyhydric alcohol. Monomers and divinylbenzene are preferred, and the poly(meth)acrylated monomers include, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate,
Polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, tetramethylolmethanetetra(meth)acrylate , pentaerythritol tri(meth)acrylate, allyl methacrylate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, etc., and one or more of these monomers can be used. . Since it is necessary to sufficiently impregnate the above monomer into the hydrosol particles, it is preferable to use a highly oil-soluble monomer from the viewpoint of the time required for impregnation and the distribution ratio. The monomer having two or more ethylenically unsaturated bonds is desirably added in an amount of 0.01 to 15 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the solid content of the hydrosol. Addition amount is 0.01
If the amount is less than 1 part by weight, sufficient intra-particle cross-linking will not take place and no significant improvement in cohesive force can be expected, and if it exceeds 15 parts by weight, intra-particle cross-linking will proceed excessively, resulting in the formation of a film. This is not preferable as it results in a brittle molded product. The polymerization initiator used in post-polymerizing the above monomers for cross-linking in the third step is not particularly limited as long as it causes radical polymerization, such as benzoyl peroxide, tert-butyl peroxide, halogen, etc. Organic peroxides such as benzoyl peroxide, azo compounds such as azobisisobutyronitrile, azobisisobutyramide, methylvaleronitrile, diazoaminoazobenzene, persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate. Salts, or combinations of these persulfates with reducing agents such as sulfites and bisulfites, redox initiators, hydrogen peroxide, etc., can be used to ensure cross-linking within hydrosol particles reliably and uniformly. It is desirable to select a hydrogen-abstracting oil-soluble initiator, such as an organic peroxide, to initiate the postpolymerization. The amount of these polymerization initiators used is 0.01 to 5 parts by weight per 100 parts by weight of the monomer used in the third step,
The amount is preferably 0.1 to 3 parts by weight. In the third step, first, a predetermined amount of the monomer having two or more ethylenically unsaturated bonds is added all at once to the copolymer hydrosolized in the second step, and the mixture is thoroughly stirred and mixed to form a hydrosol. The monomer may be impregnated into the particles, or the monomer may be sequentially added dropwise to the hydrosol particles to impregnate the monomer into the hydrosol particles. The polymerization initiator may be dissolved or dispersed in the monomer and added to the hydrosol, or may be added before or after the monomer is added to the hydrosol. The method of adding a monomer dropwise generally involves starting and proceeding the polymerization reaction at the same time as the monomer is added, paying attention to the concentration and dropping rate that will not destabilize the hydrosol. It is necessary to ensure that the polymerization proceeds uniformly. Furthermore, it is important to start the polymerization reaction after the monomer is sufficiently impregnated into the hydrosol particles.If the monomer is present in the form of oil droplets in the system, the monomer is absorbed outside the particles. Since a homopolymer of polymers is produced, intraparticle crosslinking is not performed and desired effects cannot be expected. Therefore, it is necessary to maintain the reaction system at a low temperature until the impregnation of the added monomer is completed.
After the impregnation is completed, the temperature of the reaction type is raised to 40 to 90°C when a thermally cleavable initiator is used, or to room temperature or higher when a redox type initiator is used to initiate the polymerization reaction. The hydrosol composition obtained as described above is
The hydrosol particles obtained in the second step are those obtained by addition polymerization or graft polymerization of a cross-linking monomer having two or more ethylenically unsaturated bonds, and the average particle diameter is There is almost no difference from the hydrosol particles obtained by
range, and is stably dispersed in water. The hydrosol composition of the present invention may further include an external crosslinking agent before or after the third step to improve physical properties, as well as conventional colorants, fillers, and anti-aging agents. , rust inhibitor, antibacterial agent,
Various additives such as leveling agents can be added at any step. It can also be mixed with conventional emulsion compositions and exhibits its effect as a modifier for emulsion compositions. As described above, the hydrosol composition of the present invention is produced by hydrosolizing a copolymer obtained from a specific monomer mixture, and then post-polymerizing a monomer having a specific cross-linking property inside the hydrosol particles. Because of this, the composition is highly and uniformly three-dimensional and has a crosslinked form, so when dried and formed into a film, the molded product has excellent cohesive strength.
For example, it exhibits excellent adhesive properties when used as a pressure-sensitive adhesive tape. Furthermore, although the composition of the present invention does not contain any emulsifier, it is mechanically and chemically stable due to its extremely fine particle size, and has excellent water resistance, solvent resistance, and film-forming properties when formed into a film. It is excellent. The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these and various applications are possible without departing from the technical idea of the present invention. In addition, parts in this section mean parts by weight. Example 1 In the first step, 10% by weight of a monomer mixture consisting of 80 parts of n-butyl acrylate, 20 parts of ethyl acrylate, and 10 parts of methacrylic acid was charged into a four-necked flask and stirred for about 1 hour. Nitrogen replacement was performed. Next, the inner bath temperature was raised to 65°C, and 0.1 part of benzoyl peroxide was added as a polymerization initiator to initiate polymerization, and the reaction temperature was controlled by the stirring speed, outer bath temperature, and dropping rate of the remaining monomer. Monomer dropwise polymerization was carried out for 4 hours while controlling the temperature to 70-80°C.
When no heat generation was observed, the inner bath temperature was raised to 80-90°C and aged for about 2 hours to determine the weight average molecular weight.
A copolymer of 5.2×10 ⁵ (according to GPC) was obtained. Next, in the second step, 0.25 equivalent of ammonia water (10% by weight concentration) was added to the carboxyl group of the copolymer obtained above while maintaining the inner bath temperature at 60°C and stirring thoroughly. Perform neutralization treatment,
Further water was added to invert the phase to obtain a hydrosol that was safely dispersed in water. The solid content concentration, viscosity at 25° C., and average particle size (according to Nanosizer) of the obtained hydrosol were 27% by weight, 32 poise, and 0.06 μm, respectively. In the third step, 5 parts of divinylbenzene is added at once to 100 parts of the solid content of the hydrosol obtained above while stirring under a nitrogen atmosphere to sufficiently impregnate the hydrosol particles, and then the internal bath temperature is lowered. about
The temperature was raised to 65°C, and 0.015 parts of ammonium persulfate was added as a polymerization initiator to initiate post-polymerization, and the polymerization reaction was carried out for about 3 hours to obtain a hydrosol composition of the present invention. The solid content concentration, viscosity at 25°C, and average particle diameter of the obtained hydrosol composition are respectively
It was 27% by weight, 30 poise and 0.07 μm. Example 2 2-ethylhexyl acrylate as the first step
75 parts of ethyl methacrylate, 25 parts of acrylonitrile, 5 parts of acrylic acid, and 10 parts of n-propanol were placed in a four-necked flask, and heated at 40°C with stirring for about 40 minutes. The atmosphere was replaced with nitrogen for a minute. Next, 0.15 parts of azobisisobutyronitrile was added as a polymerization initiator, and after dissolving,
Polymerization was started by increasing the inner bath temperature to 80°C, and the monomer dropwise polymerization was carried out while controlling the reaction temperature at 80 to 90°C depending on the stirring speed, outer bath temperature, and dropping rate of the remaining monomer. The weight average molecular weight was 4×10 ⁵ (GPC
) was obtained. Next, in the second step, 0.5 equivalents of ammonia aqueous solution (10% by weight) and water are added to the carboxyl groups of the copolymer obtained above to perform neutralization treatment and phase inversion to ensure stable dispersion in water. A hydrosol was obtained. The solid separation, viscosity at 25°C, and average particle size (according to Nanosizer) of the obtained hydrosol were 35% by weight, 140 poise, and 0.05 μm, respectively.
It was hot. As the third step, the hydrosol obtained above was heated to 65°C under a nitrogen atmosphere and stirred, and a mixed solution of 0.8 parts of diethylene glycol dimethacrylate and 0.0016 parts of benzoyl peroxide was added to 100 parts of solid content of the hydrosol. , was added dropwise over about 1 hour to start post-polymerization while being impregnated into the hydrosol particles, and further reacted for about 2 hours while maintaining the internal bath temperature at 70 to 80°C to obtain the hydrosol composition of the present invention. Ta. Solid content concentration of the obtained hydrosol composition,
The viscosity and average particle size at 25°C were 35% by weight, 125 poise, and 0.05 μm, respectively. Example 3 In the first step, 280 parts of a 3 x 10 ^-4 weight% polyvinyl alcohol (saponification degree 87%) aqueous solution was charged into a four-necked flask, and 2-ethylhexyl acrylate was added.
Add 70 parts of n-butyl acrylate, 20 parts of acrylonitrile, 4 parts of methacrylic acid, and 0.1 part of benzoyl peroxide, and adjust the internal bath temperature while stirring.
The temperature was raised to 70°C to start polymerization, and the reaction was carried out for about 4 hours, resulting in a weight average molecular weight of 6 x 10 ⁵ (according to GPC).
A pearl particle-like copolymer with an average particle diameter of 1.3 mm was obtained. Next, after separating the above copolymer by washing with water, filtering, and drying, as a second step, 15 parts of isopropyl alcohol was added to 100 parts of the copolymer to completely dissolve it, and the same procedure as in Example 1 was carried out. A hydrosol stably dispersed in water was obtained by neutralization and phase inversion. The solid content concentration, viscosity at 25° C., and average particle diameter (according to Nanosizer) of the obtained hydrosol were 32% by weight, 90 poise, and 0.08 μm, respectively. As the third step, a mixture of 2.0 parts of trimethylolpropane trimethacrylate, 0.01 part of potassium persulfate, and 1 part of water is added to the hydrosol obtained above at room temperature while stirring, based on 100 parts of the solid content of the hydrosol. The aqueous solution was added all at once to sufficiently impregnate the inside of the hydrosol particles, and an equimolar amount of sodium bisulfite aqueous solution (1% by weight) to the above potassium persulfate was added to initiate post-polymerization, and the reaction was carried out for about 3 hours. , a hydrosol composition of the present invention was obtained.
The solid content concentration, viscosity at 25°C, and average particle diameter of the obtained hydrosol composition were 31% by weight, respectively.
It was 58 poise and 0.08 μm. Comparative Examples 1-3 Comparative Examples 1-3 correspond to Examples 1-3,
In each example, the hydrosol composition was obtained in the first and second steps and was not subjected to intraparticle crosslinking. Comparative Example 4 A hydrosol composition containing an external crosslinking agent was obtained by replacing the third step of Example 1 as follows. To the hydrosol obtained in the second step, 4 parts of triepoxypropyl isocyanurate (trade name: TEPIC,
A hydrosol composition was obtained by adding an aqueous solution (5% by weight) (manufactured by Nissan Chemical Industries, Ltd.). In order to examine the physical properties of the hydrosol compositions obtained in each Example and Comparative Example, each composition was dried and formed into a film, and the gel fraction and retention power were measured, and the results are shown in Table 1. The drying conditions were 100° C. for 5 minutes, and the dry film thickness was 50 μm. Further, as a reference example, the physical properties of a film obtained by drying the hydrosol composition obtained in Comparative Example 4 at 150° C. for 5 minutes are also listed in Table 1.

[Table] The gel fraction and retention power in the table were measured by the method shown below. <Gel fraction> The dried film prepared from each example, comparative example, and reference example (hereinafter referred to as sample) was placed in a nylon mesh bag and boiled and refluxed in acetone for 24 hours to extract the soluble content. It was separated from the gel fraction and calculated using the following formula. Gel fraction (%) = Dry weight of sample after extraction (g) / Dry weight of sample before extraction (g) x 100 <Retention force> Samples prepared from each example, comparative example, and reference example were 50 μm thick. 10mm width x 20
A sample was attached to a length of mm, a load of 500 g was suspended from the end of the sample, and the time required for the sample to fall due to cohesive failure was measured in a thermostat at 40°C and 80°C. As is clear from Table 1, the film obtained from the hydrosol composition of the present invention has high retention and excellent internal cohesion, suggesting that the interior of the particles is highly three-dimensional. It was also found that the properties were very good compared to Comparative Example 4 and Reference Example in which an external crosslinking agent was used.

Claims (1)

[Claims] 1. 2 to 20% by weight of unsaturated monomers having acidic groups.
and 80 to 98% by weight of other acrylic unsaturated monomers that can be copolymerized with this.
The average particle size of a copolymer of 10 ⁴ to 10 ⁶ is neutralized in the presence of alkali and water and phase inverted to O/W type.
A hydrosol composition having the form of water-dispersed hydrosol particles of 0.01 to 0.1 μm, the hydrosol particles being cross-linked by a monomer having two or more ethylenically unsaturated bonds. thing. 2 2-20% by weight of unsaturated monomers having acidic groups
and 80 to 98% by weight of another acrylic unsaturated monomer that can be copolymerized with the monomer mixture to obtain a copolymer, and the copolymer is injected with alkali and By adding water to neutralize some or all of the acidic groups and inverting the phase, the average particle size is 0.01~
A second step of obtaining a hydrosol stably dispersed in 0.1 μm water, and adding 0.01 to 15 parts by weight of a monomer having two or more ethylenically unsaturated bonds to 100 parts by weight of the solid content of the hydrosol. A method for producing a hydrosol composition, comprising a third step of impregnating the hydrosol particles into hydrosol particles and then performing a cross-linking reaction.