JP2005060712A - Acrylic polymer fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastisol applicable to an industrial use, wherein the plastisol is prepared by dispersing acrylic polymer fine particles, which contain no vinyl chloride polymer and have good storage stability and good retention of a plasticizer, in a plasticizer. <P>SOLUTION: The acrylic polymer fine particles comprise primary particles P having a core shell structure consisting of a core polymer C and a shell polymer S, wherein the primary particles P have an average particle diameter of 250 nm or larger; the core polymer C and the shell polymer S are copolymers of (meta)acrylic monomer mixtures Mc and Ms respectively; and the weight proportion of Mc to Ms is 10/90-90/10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to acrylic polymer fine particles. Furthermore, the present invention relates to a plastisol obtained by dispersing acrylic polymer fine particles in a plasticizer. More specifically, the present invention relates to a plastisol having excellent storage stability and excellent plasticizer retention after heating film formation.

A plastisol obtained by dispersing polymer fine particles using a plasticizer as a medium is used in various industrial fields, and its industrial value is remarkable. In particular, plastisol using vinyl chloride polymer fine particles is known as vinyl chloride sol (hereinafter abbreviated as vinyl chloride sol). Due to its excellent physical properties, wallpaper, automotive undercoat, automotive body sealer, carpet backing material, flooring Used in a wide range of fields such as paint.
Vinyl chloride sol is a basic property required for plastisol due to the unique properties of vinyl chloride polymer fine particles.
(i) The polymer fine particles are not swollen or dissolved by the plasticizer during storage of the plastisol (hereinafter, this property is abbreviated as storage stability);
(ii) Even after plastisol is applied and a gelled product is formed by heat treatment to obtain a dried coating film, the plasticizer is well retained in the dried coating film and does not bleed out over time (hereinafter referred to as this property). Is abbreviated as plasticizer retention)
It is very excellent in the industry and has been widely used industrially as it is now.

However, products using PVC sol have been pointed out for a long time because hydrogen chloride gas is generated when incinerated, which causes serious damage to the incinerator. In recent years, the problem of acid rain caused by hydrogen chloride gas and the adverse effects on the human body and the global environment caused by dioxins, which are extremely toxic during incineration, have been regarded as problems. The appearance of alternative materials with less environmental problems was expected.
Thus, one-component urethane-based materials, epoxy-based materials, water-based emulsion materials, silicone-based materials, and the like have been proposed as candidates for materials that can substitute for vinyl chloride sols. However, in the production of these materials, it is impossible to use existing production facilities for vinyl chloride sol, and a huge investment in equipment is required for industrial use. Furthermore, one-component urethane-based materials have many problems such as poor storage stability due to thickening, toxicity problems, and high cost. Epoxy materials have many problems such as high cost and physical properties that are far below those of PVC. In the case of water-based emulsions, problems such as the inability to thickly coat, the occurrence of blistering in the coating as the medium water evaporates, and poor water resistance of the coating It is done. Silicone materials are also expensive and cannot be used as substitute materials from the viewpoint of physical properties. Therefore, it has been extremely difficult to replace PVC sol with these materials.

As an alternative material for solving such problems, a plastisol composed of acrylic polymer fine particles, that is, an acrylic sol has been proposed in recent years.
For example, Patent Document 1, Patent Document 2, and Patent Document 3 propose a novel plastisol obtained by combining a vinyl chloride polymer and an acrylic polymer. However, this plastisol essentially contains a vinyl chloride polymer, and in terms of generating harmful gas during incineration, it is not different from conventional vinyl chloride sols, and has not yet solved the above environmental problems. .
Therefore, Patent Document 4 proposes a plastisol made of an acrylic polymer as a plastisol containing no vinyl chloride polymer and other halogen-based polymer. The polymer used in the above document is a uniform structure particle, but in the case of an acrylic polymer, it is impossible to realize the storage stability of plastisol and the plasticizer retention of the coating film with the uniform structure particle. The plastisol according to the above publication tends to have extremely poor storage stability or extremely poor physical properties at the practical level.
This is because, unlike a vinyl chloride polymer, an acrylic polymer has a weak van der Waals cohesive force acting between molecules, so if a composition that is highly compatible with a plasticizer is used, the plasticizer can be easily intermolecular. This is caused by intruding into the resin and causing plasticization, that is, gelation, resulting in poor storage stability.
Therefore, in order to improve the storage stability, it is necessary to lower the compatibility with the plasticizer. However, a polymer with low compatibility with a plasticizer has good storage stability, but has a plasticizer retention property of a coating film (hereinafter abbreviated as a gelled film) obtained after applying a sol and heating to form a film. It is very low, and the plasticizer bleeds out from the gelled film over time.
Thus, in the case of acrylic sols using acrylic polymer fine particles, the relationship between storage stability and plasticizer retention after film formation is contradictory, and polymer fine particles with a uniform structure satisfy this. Was impossible.

Therefore, Patent Document 5 has been proposed as an acrylic plastisol using core-shell structured particles. Here, a polymer obtained by adding an acid or an acid anhydride to an acrylic polymer is used. However, the polymers proposed in the above documents have low compatibility with plasticizers, and in particular, since the copolymerization ratio of methyl methacrylate in the shell portion is high, plasticizers with low polarity such as phthalate ester plasticizers are used. When used, the plasticized state becomes poor and a good coating film cannot be obtained.
In addition, Patent Document 6 proposes a plastisol using core-shell structured particles. Here, even if the core-shell structured particles are used, uniform structured particles are produced, and this is subsequently subjected to an alkali hydrolysis treatment to convert ester groups on the very surface layer of the particles into carboxyl groups. Therefore, the thickness of the shell portion is extremely thin, and is substantially only about 1% or less of the volume of the particles. Therefore, the improvement effect of the storage stability expected as the role of the shell portion is extremely low. In addition, the shell portion introduced by alkali hydrolysis has a very high acid value, has very low compatibility with the plasticizer, and remarkably deteriorates the film formability. In addition, such a high acid value shell part contributes to the polymer particles creating a structural viscosity in the plastisol, and thus has a detrimental effect such as an increase in the viscosity of the plastisol and a decrease in workability.

Another example of plastisol using core-shell structured particles is proposed in Patent Document 7. Here, a technique of obtaining a core-shell structure by stepwise polymerizing monomers having different compositions is used. Here, in order to express the storage stability of plastisol, a shell that is incompatible with a plasticizer is used, and a shell obtained by copolymerizing 80% by weight or more of methyl methacrylate, which has low compatibility with many plasticizers. Is used. However, a shell with very low compatibility is advantageous in terms of storage stability, but the sol film formability, strength of the resulting coating film, elongation, transparency, adhesion to the substrate, soundproofing, vibration damping Such a tendency tends to be inferior in various performances, and in particular, inferior in plasticizer retention, bleed-out is likely to occur and is not practical.
Further examples of plastisol using core-shell structured particles are proposed in Patent Document 8 and Patent Document 9. Here, a very basic performance is realized by using a core-shell polymer consisting essentially of a core portion that is compatible with a plasticizer and a shell portion that is incompatible with a plasticizer. However, extremely high physical properties are required for industrial practical use. In that respect, the polymer proposed in the above publication is not optimized in the balance of compatibility with the plasticizer. In addition, both the storage stability and the plasticizer retention of the coating film are at a low level, which is not suitable for industrial practical use.
As described above, various studies have been made on acrylic sol in order to achieve both storage stability and plasticizer retention, which are the most basic properties of plastisol. The current situation is that the practical level has not been reached.
JP 60-258241 A JP-A 61-185518 JP 61-207418 A JP-A-5-255563 JP-A-5-279539 JP-A-6-322225 JP-A-53-144950 JP-A-7-233299 JP-A-8-295850

  An object of the present invention is to provide a new plastisol that does not contain a vinyl chloride polymer, has good storage stability, and good plasticizer retention at a level that can be industrially used.

As a result of intensive studies to solve the above problems, the present inventors have obtained an acrylic sol excellent in both storage stability and plasticizer retention by increasing the particle diameter of the acrylic polymer fine particles. In addition, by using an acrylic polymer having a core-shell structure having a primary particle size of 250 nm or more, the monomer composition of the shell portion is specified, and the compatibility between the polymer and the plasticizer is controlled, so that the storage stability and the plasticizer The present inventors have found that the balance of retention can be improved to an industrially usable level, and the present invention has been completed.
That is, the gist of the present invention is as follows:
(i) acrylic polymer fine particles composed of primary particles P having a core-shell structure composed of a core polymer C and a shell polymer S, the average particle diameter of the primary particles P being 250 nm or more, and the core polymer C and The shell polymer S is a copolymer of the monomer mixture Mc and Ms shown below, respectively, and the acrylic polymer fine particles having a weight ratio of Mc and Ms of 10/90 to 90/10:
Mc: the total is 100 mol%,
Methyl methacrylate 20-85 mol%
(Meth) acrylic acid ester of C2-C8 aliphatic alcohol and / or aromatic alcohol
15 to 80 mol%, and other copolymerizable monomers 30 mol% or less Ms: the total is 100 mol%,
Methyl methacrylate 20-79.5 mol%
(Meth) acrylic acid ester of C2-C8 aliphatic alcohol and / or aromatic alcohol
5-40 mol%
Carboxyl group or sulfonic acid group-containing monomer
0.5 to 10 mol%, and other copolymerizable monomers 30 mol% or less
(ii) (1) A) A single amount which has a solubility of 0.02% by mass or more with respect to the medium at 20 ° C. in a medium mainly containing water, and the polymer does not dissolve in the medium. In a state where the emulsifier micelle is not present in the medium, and using a water-soluble radical polymerization initiator to obtain a polymer dispersion.
B) a step of obtaining a polymer dispersion coated by dropping the monomer mixture with respect to the polymer dispersion;
(2) a step of recovering polymer fine particles by spray drying the above polymer dispersion;
A method for producing acrylic polymer fine particles comprising:

In this specification, (meth) acrylic acid represents acrylic acid and / or methacrylic acid, and (meth) acrylate represents acrylate and / or methacrylate.
In the present specification, “primary particles” refer to particles of a minimum unit constituting polymer fine particles.
The acrylic polymer fine particles of the present invention are composed of primary particles P having a core-shell structure. The reason for using the core-shell structure is that, in the case of an acrylic polymer, the storage stability and the plasticizer retention cannot be achieved in a uniform structure. Explaining this in detail, unlike vinyl chloride polymers, acrylic polymers have weak van der Waals cohesive forces acting between molecules, so if a composition that is highly compatible with plasticizers is used, the plasticizer can easily be It is because it penetrates in between and causes plasticization, that is, gelation, resulting in poor storage stability. Therefore, in order to improve the storage stability, it is necessary to lower the compatibility with the plasticizer. However, a polymer having low compatibility with a plasticizer has good storage stability, but the plasticizer retention of the gelled product after heating is extremely low, and the plasticizer bleeds out over time. That is, in the case of an acrylic polymer, the relationship between storage stability and plasticizer retention is contradictory, and it is impossible to satisfy this with a polymer having a uniform structure.
On the other hand, in the polymer having a core-shell structure, if the core polymer C has a composition highly compatible with the plasticizer and the shell polymer S has a composition low in compatibility with the plasticizer, the above These conflicting issues are solved to some extent. In other words, during storage, the shell polymer that completely surrounds the polymer has good storage stability to prevent swelling and dissolution by the plasticizer. Conversely, after heating, the core-shell structure is broken due to active molecular motion. For this reason, the plasticizer retainability is improved due to the high compatibility of the core.

The core-shell structure referred to in the present invention refers to a structure obtained by seed polymerization of monomer mixtures having different compositions in several stages. The “seed polymerization” refers to a polymerization method in which polymer particles prepared in advance are used as seeds, and the monomer is absorbed and polymerized to grow the particles. Therefore, it must be clearly technically distinguished from polymer particles in which particles having a uniform structure are produced in advance by emulsion polymerization, fine suspension polymerization or the like, and surface-modified by post-treatment such as alkali hydrolysis.
The first reason is that, in the method of surface modification by post-treatment such as alkaline hydrolysis, only a thin modification layer is introduced only in the surface layer portion of the particle, and the present invention is intended for its physical thickness. This is because a shell having a sufficient thickness is essentially different.
Specifically, in the present invention, the thickness of the shell portion is not particularly limited, but is preferably about 10% or more of the primary particle diameter.
For example, when the particle size is 600 nm and the core / shell weight ratio is 50/50, theoretically, the physical thickness of the shell is about 62 nm, and this value sets the size of the polymethyl methacrylate molecule to 0.5 nm. In some cases, the thickness is over 120 molecules, and when this thick shell is used as a plastisol, it prevents the plasticizer from entering the polymer fine particles and contributes to the development of good storage stability.
On the other hand, when the surface modification layer is introduced by subjecting the uniformly structured particles to an alkali hydrolysis treatment, when the particle diameter is 600 nm, it is about 10 nm or at most about 20 nm. This is only a few tens of centimeters in thickness of the methyl methacrylate molecule, and it is practically impossible to impart storage stability of the plastisol with such a thin surface modification layer. Further, even if further alkaline hydrolysis is performed, the surface modification layer produced by the hydrolysis has an extremely high acid value, exhibits water solubility, and the polymer fine particles dissolve in the aqueous phase without being fixed as particles. Therefore, it is impossible to introduce a surface modification layer that can be said to be a sufficiently thick shell.

The second reason is that the surface modification layer introduced by alkali hydrolysis or the like is extremely difficult to freely control the composition, particularly the acid value, and is used for this application where importance is attached to compatibility with the plasticizer. Is inappropriate.
In the present invention, particularly when the surface modification layer is introduced by seed polymerization, the composition of the shell can be arbitrarily controlled. Therefore, the compatibility with the plasticizer and the glass transition temperature, which are important for the plastisol, are optimized. It is possible to On the other hand, when the surface modification layer is introduced by post-treatment such as alkaline hydrolysis of the uniform structure particles, the composition is such that only the surface layer portion of the polymer particles has a very high acid value, The composition cannot be controlled with the thickness.
The average particle diameter of the primary particles P having a core-shell structure needs to be 250 nm or more.
As described above, although the balance between the storage stability of plastisol and the plasticizer retention of the coating film can be adjusted to some extent by using the core-shell structure, in order to further increase this to a level that can be used industrially, It is necessary to make the total surface area of the primary particles smaller and the shell to have a certain thickness or more. That is, it is necessary to increase the particle diameter of primary particles having a core-shell structure, and the range is 250 nm or more in terms of average particle diameter. When the average particle size is smaller than this, the storage stability and plasticizer retention balance are better than those of a polymer having a uniform structure, but the strict storage stability required industrially, for example, 35 ° C. × 2 weeks. The required standard cannot be satisfied, and workability deteriorates due to thickening.

The monomer mixture Mc which gives the core polymer C has a methyl methacrylate of 20 to 85 mol%, a C2 to C8 aliphatic alcohol and / or a (meth) acrylic ester of an aromatic alcohol when the total amount of monomers is 100 mol%. It is necessary that 15 to 80 mol% and other copolymerizable monomers are composed of 30 mol% or less.
When methyl methacrylate is less than 20 mol%, or when C2-C8 aliphatic alcohol and / or (meth) acrylic acid ester of aromatic alcohol is more than 80 mol%, the core polymer (C) itself has a low Tg. As a result, the compatibility of the core polymer (C) with the plasticizer becomes too high, so that the gelled product obtained by heating has a very low Tg and causes problems such as stickiness. In this case, even if the core-shell ratio and the primary particle size are changed, the storage stability of plastisol becomes poor, which is not suitable for practical use.
When the methyl methacrylate is more than 85 mol%, or when the C2-C8 aliphatic alcohol and / or the (meth) acrylic acid ester of the aromatic alcohol is less than 15 mol%, the compatibility of the core polymer with the plasticizer is low. Thus, the plasticizer retention, which is the original purpose of the core polymer, is lowered, and the gelled product after heating bleeds out the plasticizer over time.
For the core polymer, other copolymerizable monomers can be arbitrarily used within a range of 10 mol% or less. As such a copolymerizable monomer, a monomer having the performance required for plastisol, for example, the ability to be added in terms of adhesion to a substrate, reactivity, etc., can be used as appropriate.

A preferable composition of the monomer mixture Mc is that when the total amount of monomers is 100 mol%, methyl methacrylate is 20 to 70 mol%, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth) acrylate. One or more (meth) acrylic acid esters selected from the group consisting of 30 to 80 mol% and other copolymerizable monomers are 20 mol% or less.
A more preferable composition is that when the total amount of monomers is 100 mol%, methyl methacrylate is 20 to 70 mol%, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth) acrylate. 30 to 80 mol% of one or more kinds of (meth) acrylic acid ester selected and 10 mol% or less of other copolymerizable monomers.
In the case of these preferred compositions, the balance between storage stability and plasticizer retention is further improved, and plastisol can be obtained that satisfies the very strict storage stability requirement of 40 ° C. × 2 weeks, and is formed into a film. The strength and elongation of the coating film thus obtained are very excellent.

Furthermore, the cost can be reduced by using (meth) acrylic acid ester of C4 alcohol which is easily available industrially, which is industrially advantageous.
The acrylic polymer fine particles used in the acrylic sol have a large primary particle size, so when compared with particles of the same weight and a small particle size, the contact area with the plasticizer is small. Can maintain the storage stability, and can compensate for the film forming components other than MMA by the reduced amount. The plasticizer retention at the time of film formation and the storage stability of the acrylic polymer fine particles in the sol Both improve.
The monomer mixture Ms that gives the shell polymer S is a (meth) acrylic acid of 20 to 79.5 mol% of methyl methacrylate and a C2 to C8 aliphatic alcohol and / or aromatic alcohol when the total amount of monomers is 100 mol%. It is necessary that the ester is composed of 5 to 40 mol%, the carboxyl group or sulfonic acid group-containing monomer is 0.5 to 10 mol%, and the other copolymerizable monomer is composed of 30 mol% or less.

When the amount of methyl methacrylate is less than 20 mol%, or when the amount of (meth) acrylic acid ester of C2-C8 aliphatic alcohol and / or aromatic alcohol is more than 40 mol%, the phase of the shell polymer (S) with respect to the plasticizer Since the solubility is increased and the storage stability, which is the original purpose of the shell polymer, is poor, the basic performance of the acrylic sol, such as gelation during the plastisol manufacturing operation, tends to be poor.
When the methyl methacrylate is more than 79.5 mol%, or when the C2-C8 aliphatic alcohol and / or (meth) acrylic acid ester of the aromatic alcohol is less than 5 mol%, the compatibility of the shell polymer is lowered. Therefore, the storage stability is good, but the plasticizer retainability of the coating film after gelation by heating is insufficient, and the plasticizer tends to bleed out over time.

In the present invention, a carboxyl group- or sulfonic acid group-containing monomer is used to improve the storage stability of the plastisol of the present invention and the dispersibility of the polymer fine particles in the sol.
When the carboxyl group and / or sulfonic acid group-containing monomer is less than 0.5 mol%, the compatibility of the shell polymer with the plasticizer is increased, so that the storage stability tends to be poor.
Further, the dispersion state of the polymer fine particles in the plasticizer is changed, the viscosity of the plastisol is increased, and workability tends to be poor, which is not preferable.
In addition, when the carboxyl group and / or sulfonic acid group-containing monomer is more than 10 mol%, the compatibility of the shell polymer with the plasticizer is too low. The plasticity becomes poor and the plasticizer bleeds out over time from the gelled product, which is inappropriate.
Further, the gelled product tends to become brittle, and the strength of the coating film tends to decrease. Furthermore, the water resistance of the gelled product tends to decrease, which is not preferable.
In the shell polymer, other copolymerizable monomers can be arbitrarily used within a range of 30 mol% or less. As such a copolymerizable monomer, a monomer having the performance required for plastisol, for example, the ability to be added in terms of adhesion to the substrate, reactivity, etc., can be used as appropriate.

As a preferable composition of the monomer mixture Ms, when the total amount of monomers is 100 mol%, methyl methacrylate is 30 to 79.5 mol%, n-butyl (meth) acrylate, i-butyl (meth) acrylate and t-butyl (meta ) One or more (meth) acrylic acid ester selected from the group consisting of acrylate is 5 to 40 mol%, carboxyl group-containing acrylic monomer is 0.5 to 10 mol%, and other copolymerizable monomers are 20 mol% or less. It is.
A more preferable composition is that when the total amount of monomers is 100 mol%, methyl methacrylate is 55 to 79.5 mol%, and includes n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth) acrylate. One or more (meth) acrylic acid esters selected from the group are 20 to 40 mol%, carboxyl group-containing acrylic monomers are 0.5 to 10 mol%, and other copolymerizable monomers are 10 mol% or less.
In the case of these preferred compositions, the balance between the storage stability of plastisol and the plasticizer retention of the coating film is further improved, and a plastisol that satisfies even more stringent storage stability requirements such as 40 ° C. × 2 weeks is obtained. The strength and elongation of the coating film obtained by forming this film is very excellent.

Furthermore, it is possible to reduce the cost by using (meth) acrylic acid ester of C4 alcohol which is easily available industrially or carboxyl group-containing acrylic monomer, which is industrially advantageous.
The weight ratio of the monomer mixture Mc giving the core polymer C and the monomer mixture Ms giving the shell polymer S needs to be 10/90 to 90/10.

When the ratio of the core polymer is lower than 10% by weight or when the ratio of the shell polymer is higher than 90% by weight, the amount of the core polymer which is a component for holding the plasticizer is too small. In this case, the plasticizer retention is insufficient and the plasticizer bleeds out over time. Alternatively, in a severe case, the compatibility with the plasticizer is too low, so that the gelation itself becomes impossible even when heated.
When the ratio of the core polymer is more than 90% by weight, or when the ratio of the shell polymer is less than 10% by weight, the amount of the shell polymer, which is a component that imparts storage stability, is too small. The coalescence is swollen or dissolved by the plasticizer, causing a serious problem that the plastisol is thickened or gelled.
A preferable range of the weight ratio of the monomer mixture Mc to the monomer mixture Ms is 30/70 to 70/30. Within this range, a balance between storage stability and plasticizer retention is further suitable, and a plastisol that can satisfy the more severe storage stability requirement of 40 ° C. × 2 weeks can be obtained.

The (meth) acrylic acid ester of C2 to C8 aliphatic alcohol and / or aromatic alcohol used in the present invention is not particularly limited. For example, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meta ) Acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid esters of linear aliphatic alcohols such as octyl (meth) acrylate, or cyclohexyl (meth) (Meth) acrylic acid esters of cyclic aliphatic alcohols such as acrylates, (meth) acrylic acid esters of aromatic alcohols such as phenyl (meth) acrylates and benzyl (meth) acrylates can be used. Among these, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth) acrylate are preferably used. These monomers can be easily obtained and are significant in terms of industrial practical use.
The carboxyl group- or sulfonic acid group-containing monomer used in the present invention is not particularly limited. For example, methacrylic acid, acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, methacrylic acid 2-succinoloyloxyethyl-2- Methacryloyloxyethyl succinic acid, methacrylic acid 2-malenoyloxyethyl-2-methacryloyloxyethyl maleic acid, methacrylic acid 2-phthaloyloxyethyl-2-methacryloyloxyethyl phthalic acid, methacrylic acid 2-hexahydrophthaloyloxy A carboxyl group-containing monomer such as ethyl-2-methacryloyloxyethyl hexahydrophthalic acid, a sulfonic acid group-containing monomer such as allyl sulfonic acid, and the like can be used. Preferred are methacrylic acid and acrylic acid, which are industrially inexpensive and can be easily obtained, and have good copolymerizability with other acrylic monomer components and are also preferred from the viewpoint of productivity.

These acid group-containing monomers may be in the form of a salt such as an alkali metal, and examples thereof include potassium salts, sodium salts, calcium salts, zinc salts, and aluminum salts. These can be in the form of a salt when polymerized in an aqueous medium, or can be in the form of a salt after polymerization.
Examples of other copolymerizable monomers used in the core polymer and shell polymer of the present invention include (meth) acrylates of C9 or higher alcohols such as lauryl (meth) acrylate and stearyl (meth) acrylate; Carbonyl group-containing (meth) acrylates such as chiethyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, hydroxyl group-containing (meth) acrylates such as 2-hydroxypropyl (meth) acrylate; glycidyl (meth) acrylate Epoxy group-containing (meth) acrylates such as: N-dimethylaminoethyl (meth) acrylate, amino group-containing (meth) acrylates such as N-diethylaminoethyl (meth) acrylate; (poly) ethylene glycol di (meth) acrylate , Polyfunctional (meth) acrylates such as pyrene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate; diacetone acrylamide, N-methylol acrylamide, N-methoxy Acrylamide and its derivatives such as methyl acrylamide, N-ethoxymethyl acrylamide and N-butoxymethyl acrylamide; styrene and its derivatives; vinyl acetate; urethane-modified acrylates; epoxy-modified acrylates; silicone-modified acrylates are widely available , Can be used properly according to the application.

As plasticizers used in the present invention, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, etc., alkyl benzyl phthalates such as butyl benzyl phthalate, alkyl aryl phthalates , Dibenzyl phthalate, diaryl phthalate, tricresyl phosphate, triaryl phosphate, trialkyl phosphate, alkylaryl phosphate, adipic acid ester, ether, polyester, epoxidized soybean oil Soybean oil-based and the like can be used. These can be blended according to the physical properties required for the plastisol, such as characteristics according to each plasticizer, that is, cold resistance, flame resistance, oil resistance, low viscosity, low thixotropy and the like.
Of these, phthalate plasticizers are preferred from the viewpoints of being inexpensive and easy to obtain industrially, workability, low toxicity, and the like.
These plasticizers can be used alone or in combination of two or more plasticizers depending on the purpose.

The method for producing the acrylic polymer fine particles of the present invention is not particularly limited as long as the composition and structure described above can be obtained. For example, core-shell type particles are prepared by seed polymerization, and this is spray-dried (spray-drying) or coagulated. Examples thereof include a method of recovering solid content by a method.
In order to obtain core-shell particles of 250 nm or more, a method of growing particles by repeating seed polymerization many times, a method of obtaining by soap-free polymerization, a method of limiting the amount of emulsifier, an emulsifier with weak emulsifying power, or a protective colloid, etc. The method of using can be widely used.
Among these, it is preferable to use seed polymerization in which seed particles having a relatively large particle diameter are prepared by soap-free polymerization, and a monomer mixture having an arbitrary composition is successively added thereto. It is a simple method.
More preferably, in a medium containing water as a main component, a monomer having a solubility of not less than 0.02% by mass with respect to the medium at 20 ° C. and the polymer does not dissolve in the medium, Polymerization was carried out using a water-soluble radical polymerization initiator in the absence of emulsifier micelles to prepare a polymer dispersion, and the monomer mixture was added dropwise to the above polymer dispersion and coated. A method for obtaining a polymer dispersion is preferred.

This is because soap-free polymerization itself is extremely difficult to proceed in the case of a monomer having a solubility of less than 0.02% by mass with respect to the medium. Further, when the polymer obtained from the monomer is dissolved in the medium, the particles are not formed, so that the polymer particles cannot be obtained in the first place. Needless to say, the presence of emulsifier micelles in the medium is of course inappropriate because it deviates from the definition of soap-free polymerization. Use of this method is advantageous because it is industrially simple, suppresses the generation of scales and the generation of new particles, and stably obtains the intended particles.
The acrylic polymer fine particles of the present invention are not particularly limited as long as the secondary or higher order structure is composed of the primary particles P having a core-shell structure. For example, the primary particles are agglomerated with a weak cohesive force, strong agglomeration It is possible to take secondary structures such as particles aggregated by force and particles fused to each other by heat. Furthermore, these secondary particles can have a higher order structure by processing such as granulation. Is possible. These higher order structures can be carried out for the purpose of improving workability, for example, by suppressing the dusting of fine particles or increasing fluidity, or by improving the dispersion state of fine particles with respect to the plasticizer. It can also be done for improvement and can be designed according to application and requirements.

In the primary particles P having a core-shell structure used in the present invention, the core polymer C and the shell polymer S can be grafted together by a graft crossing agent. In this case, allyl methacrylate or the like can be used as the graft crossing agent.
In the primary particles P having a core-shell structure used in the present invention, the core polymer C and / or the shell polymer S may be crosslinked. As the crosslinkable monomer in this case, the above-described polyfunctional monomer can be used. In addition to the polyfunctional monomer, it is also possible to use ionic crosslinking with a carboxyl group or a sulfonic acid group by adding a bivalent or higher-valent alkali metal or a polyfunctional amine.
Various additives (materials) can be blended in the plastisol of the present invention depending on the application. For example, calcium carbonate, aluminum hydroxide, palita, clay, colloidal silica, mica powder, silica sand, diatomaceous earth, kaolin, talc, pennite, glass powder, fillers such as aluminum oxide, pigments such as titanium oxide and carbon black, mineral terpenes, Diluting agents such as mineral spirits, antifoaming agents, antifungal agents, deodorants, antibacterial agents, surfactants, lubricants, UV absorbers, fragrances, foaming agents, leveling agents, adhesives, etc. can be freely blended It is.

  The plastisol of the present invention can be applied to a metal or metal substrate with a thickness of 5 μm to 5 mm by a known method such as dipping, spraying, brushing, or doctoring, and gelled at a temperature of 90 ° C. to 200 ° C. . Moreover, a molded object can also be manufactured by gelatinizing in a suitable type | mold.

Hereinafter, the present invention will be described with reference to examples. The evaluation methods in the examples are as follows. Hereinafter, “part” represents “part by weight”.
Plastisol viscosity After the obtained plastisol was kept at 25 ° C. in a thermostatic water bath, the viscosity (unit: Pa · S) after 1 minute at a rotational speed of 5 rpm was measured using an E-type viscometer, as follows: evaluated.
○: Less than 30 Δ: 30 or more and less than 50 ×: 50 or more Storage stability The plastisol was kept warm in a constant temperature bath of 40 ° C., taken out after one week, and the viscosity was measured again. The viscosity increase rate of plastisol was calculated as follows (unit:%) and evaluated.
(Viscosity after storage / initial viscosity) x 100 (%)
◎: Less than 20 ○: 20 or more and less than 40 Δ: 40 or more and less than 100 ×: 100 or more

Preparation of gelled coating film and measurement of strong elongation Plastisol was applied to a glass plate with release paper on a thickness of 2 mm and gelled by heating at 140 ° C. for 20 minutes to obtain a uniform coating film. After peeling this from the glass plate, it was cut into 15 mm width × 80 mm length, and 15 mm from each end was used as the gripping part, and the tensile strength was measured with a Tensilon measuring instrument. The test speed was 200 mm / min (unit: strength MPa, elongation%). Evaluation was performed as follows.
Strength ◎: 1.0 or more ○: 0.8 or more and less than 1.0 Δ: 0.4 or more and less than 0.8 ×: Less than 0.4 Elongation ◎: 300 or more ○: 250 or more and less than 300 Δ: 100 or more and 250 Less than x: Less than 100 Plasticizer retention 2 parts of acrylic polymer fine particles and 4 parts of dioctyl phthalate (DOP) were uniformly mixed, poured into an aluminum dish, and gelled by heating at 140 ° C. for 20 minutes. This was once allowed to cool to room temperature, and then stored in a constant temperature bath at 40 ° C. for 2 weeks, and the presence or absence of bleed out of the plasticizer from the gelled product was judged visually and by touch.
○: No bleed out ×: With bleed out

Examples 1-13
Production of polymer fine particles A1 to A12 1414 g of pure water was put into a 5 liter four-necked flask equipped with a thermometer, nitrogen gas introduction tube, stirring rod, dropping funnel, and cooling tube, and nitrogen gas was thoroughly bubbled for 30 minutes. Then, the dissolved oxygen in the pure water was replaced. After stopping nitrogen gas ventilation, 45.6 g of methyl methacrylate and 34.9 g of n-butyl methacrylate were added, and the temperature was raised to 80 ° C. while stirring at 150 rpm. When the internal temperature reached 80 ° C., 0.70 g of potassium persulfate dissolved in 28 g of pure water was added all at once, and soap-free polymerization was started. Stirring was continued for 60 minutes at 80 ° C. to obtain a seed particle dispersion.
Subsequently, a monomer emulsion (methyl methacrylate 420.8 g, n-butyl methacrylate 348.16 g, sodium dialkylsulfosuccinate (trade name: Perex O-TP) 7.00 g) was added to the seed particle dispersion. Then, 350.0 g of pure water mixed and emulsified with emulsification) was added dropwise over 2.5 hours, and stirring was continued at 80 ° C. for 1 hour to obtain a polymer dispersion.
Subsequently, a monomer emulsion (methyl methacrylate 533.1 g, n-butyl methacrylate 199.1 g, methacrylic acid 24.08 g, sodium dialkylsulfosuccinate (trade name: Perex O, manufactured by Kao Corporation) was added to this polymer dispersion. -TP) 7.00 g and 350.0 g of pure water mixed and stirred for emulsification) were added dropwise over 2.5 hours, followed by continued stirring at 80 ° C. for 1 hour to obtain a polymer dispersion. It was.
After cooling the obtained polymer dispersion to room temperature, using a spray dryer (L-8 type, manufactured by Okawahara Kako Co., Ltd.), the inlet temperature is 170 ° C., the outlet temperature is 75 ° C., and the atomizer speed is 25000 rpm. Spray drying was performed to obtain polymer fine particles A1.
Similarly, acrylic polymer particles A2 to A12 having the composition shown in Table 1 were produced.

Preparation of plastisol Weigh 140 parts of dioctyl phthalate (DOP) and 100 parts of calcium carbonate to 100 parts of each of the obtained acrylic polymer fine particles A1-A12 and stir with a disper mixer (about 2000 rpm × 2 minutes) And degassing under reduced pressure to obtain uniform plastisols.
These acrylic polymer particles A1 to A12 were blended according to the blending recipe in Table 2 to obtain plastisols. The obtained plastisol was evaluated. The results are also shown in Table 2.

Examples 1 to 13 are examples using n-butyl methacrylate or i-butyl methacrylate as a methacrylic acid ester of a C4 aliphatic alcohol. In either case, di-2-ethylhexyl phthalate or di-i-nonyl phthalate is used as the dialkyl phthalate plasticizer. In any case, the composition of each monomer is changed within the most preferable range. Example 5 is a case where 2-hydroxyethyl methacrylate is used as the other monomer in the shell polymer. Examples 6 to 8 are examples using core-shell structured particles having a particle diameter exceeding 1000 nm. Example 9 is a case where styrene is used as another monomer. In Example 10, ethylene glycol dimethacrylate, which is a bifunctional monomer, was used as the other monomer. Example 11 is a case where N-butoxymethylacrylamide which is a reactive monomer is used as another monomer. In Example 12, allyl methacrylate was used as the other monomer. Example 13 is a case where the same polymer A1 as in Example 1 is used and a blocked isocyanate is blended as an additive.
In any case, the physical properties were good, and in particular, the storage stability of plastisol, the strength and elongation of the coating film were very excellent.

Comparative Examples 1-9
Polymer fine particles A′1 to A′9 having the composition shown in Table 1 were produced in the same manner as in Example 1, and plastisol was similarly prepared according to the formulation shown in Table 2. The evaluation results of the plastisol are also shown in Table 2.
Comparative Example 1 is an example (A′1) in which the ratio of the shell polymer is increased to 95%. In this case, since there are too few core polymers having good compatibility with the plasticizer, The agent bleeded out over time, and the plasticizer retention was poor. Comparative Example 2 is an example (A'2) in which the ratio of the core polymer is increased to 95%. In this case, gelation proceeds as soon as it is blended with the plasticizer, and the storage stability is extremely poor. It was not able to be evaluated as a gelled coating film. Comparative Example 3 is an example (A′3) in which nBMA, which is a methacrylic ester of C4 aliphatic alcohol of the core polymer, is reduced to 10 mol%. In this case, the compatibility of the core polymer with the plasticizer is significantly reduced. Therefore, the plasticizer bleeded out from the gelled material over time, and the plasticizer retention was poor. Comparative Example 4 is a case where nBMA, which is a methacrylic ester of C4 aliphatic alcohol of the shell polymer, is reduced to 2 mol% (A′4). In this case as well, the plasticizer bleeds out, and the plasticizer Retention was poor. Comparative Example 5 is an example (A′5) in which nBMA, which is a methacrylic ester of C4 aliphatic alcohol of the core polymer, is increased to 85 mol%. In this case, the compatibility of the core polymer with the plasticizer is remarkably increased. However, the storage stability is extremely poor because it exceeds the preferred range. Comparative Example 6 is the case where nBMA, which is a methacrylic ester of C4 aliphatic alcohol of the shell polymer, is increased to 45 mol% (A'6). Since the shell should be highly compatible, gelation proceeded immediately after blending the plasticizer, storage stability was extremely poor, and it was not possible to evaluate as a gelled coating film. Comparative Example 7 is an example (A′7) in which methacrylic acid, which is a carboxyl group-containing monomer of the shell polymer, is reduced to 0.2 mol%. In this case, the dispersion state of the polymer fine particles in the plasticizer is The viscosity of the plastisol was high and became defective. Comparative Example 8 is an example (A′8) in which the methacrylic acid, which is a carboxyl group-containing monomer of the shell polymer, is increased to 12 mol%. In this case, the compatibility with the plasticizer is significantly reduced, and the gelation state Became defective and the strength decreased. Moreover, bleed out occurred and plasticizer retention was poor. Comparative Example 9 is a case where the primary particle having a core-shell structure has a particle size of 80 nm (A'9) (in this case, the product name: PELEX SS-H is used as an emulsifier instead of Flakes Marcel) ) In this case, the total surface area of the primary particles is greatly increased and the thickness of the shell polymer that protects the core polymer from being dissolved by the plasticizer is insufficient, so that the storage stability is lowered and it can withstand practical use. I couldn't.

Comparative Examples 10-12
According to the examples shown in JP-A-7-233299, polymer particles A′10 to A′12 having the composition shown in Table 1 were produced, and plastisol was prepared according to the formulation shown in Table 2 as in Example 1. Was prepared. The evaluation results of the plastisol are also shown in Table 2.
Comparative Examples 10 to 12 are cases where the polymers (A′10 to A′12) proposed by JP-A-7-233299 were used. Comparative Examples 10 and 11 gave a good plastisol in the initial state, but the ratio of methyl methacrylate was too high, so when a dialkyl phthalate plasticizer was used, the compatibility between the coating film and the plasticizer was low. The elongation and the plasticizer retention were not sufficient. In Comparative Example 12, since the methyl methacrylate ratio of the core polymer is too high, and the carboxylic acid or sulfonic acid group-containing monomer is not used in the shell polymer, the storage stability of the plastisol is low, and the coating film physical properties are evaluated. Did not come.
Comparative Examples 13-14
According to the examples shown in JP-A-8-295850, polymer particles A′13 to A′14 having the compositions shown in Table 1 were produced, and plastisol was prepared according to the formulation shown in Table 2 as in Example 1. Was prepared. The evaluation results of the plastisol are also shown in Table 2.
Comparative Examples 13 to 14 are cases (A′13 to A′14) in which the polymers proposed by JP-A-8-295850 are used. In Comparative Example 13, since the methyl methacrylate ratio of the shell polymer was too high, the storage stability was good, but the film elongation and plasticizer retention were poor. In Comparative Example 14, since the methyl methacrylate ratio of the core was too low, the storage stability was poor, and the physical properties of the coating film were not evaluated.
Comparative Examples 15-16
According to the examples shown in JP-A-5-279539, polymer particles A′15 to A′16 having the compositions shown in Table 1 were produced, and plastisol was prepared according to the formulation shown in Table 2 in the same manner as in Example 1. Was prepared. The evaluation results of the plastisol are also shown in Table 2.
Comparative Examples 15 to 16 are cases (A′15 to A′16) in which the polymers proposed by JP-A-5-279539 are used. In either case, since the methyl methacrylate ratio of the shell polymer is too high, it cannot be plasticized with di-2-ethylhexyl phthalate, and here it is blended with dioctyl phthalate. In all cases, the initial viscosity was good, but the storage stability was poor. Moreover, the intensity | strength of the coating film was a little low and it was defect.

Comparative Examples 17-20
According to the examples shown in JP-A-5-255563, polymer particles A′17 to A′20 having the compositions shown in Table 1 were produced, and plastisol was prepared according to the formulation shown in Table 2 in the same manner as in Example 1. Was prepared. The evaluation results of the plastisol are also shown in Table 2.
Comparative Examples 17 to 20 are cases (A′17 to A′20) in which the polymer proposed by JP-A-5-255563 is used. The polymer proposed in this publication is not a core-shell structured particle but a uniform structured particle, which differs in particle structure from that intended by the present invention. The plasticizer used when blending plastisol was the one shown in the above publication. In Comparative Example 17, the storage stability was poor, and the coating film strength was slightly poor. In Comparative Example 18, the storage stability was poor. In Comparative Example 19, the compatibility between the polymer and the plasticizer was too high, the storage stability was poor, and the strength of the coating film was low.

Comparative Examples 21-24
According to the examples disclosed in JP-A-6-322225, polymer particles A′21 to A′24 having the compositions shown in Table 1 were produced, and plastisol was prepared according to the formulation shown in Table 2 in the same manner as in Example 1. Was prepared. The evaluation results of the plastisol are also shown in Table 2.
Comparative Examples 21 to 24 are cases (A′21 to A′24) in which the polymer proposed by JP-A-6-322225 is used. In this publication, it is stated that the core-shell structured particles are used. However, the core-shell structured particles referred to here are produced by first producing uniform structured particles made of an acrylic resin, and hydrolyzing the ester bonds on the surface of the particles, thereby bringing the particles to the particle surface. Only the carboxyl group is introduced. When polymer particles are alkali-treated under the conditions of the above publication, the ester bond to be hydrolyzed is in the range of about several nm from the particle surface. Therefore, the ratio of the shell polymer is greatly different from the core-shell structure particles referred to in the present invention, and in the case of the present invention, it is 30 to 70 mol% of the polymer particles. It is. In particular, considering that the average particle size of the polymer particles used in the above publication is about 2 microns, the particle surface area with respect to the particle volume is very small, so the actual ratio of the shell polymer is 1 mol% or less. Is calculated to be Therefore, in Table 1, the core-shell ratio is described as 99/1.
In the case of Comparative Examples 21 to 22, since the composition is mainly composed of methyl methacrylate, it is necessary to use a plasticizer with high polarity in order to plasticize it well, and a dialkyl phthalate plasticizer with a short alkyl chain is used. Used. Therefore, the storage stability of plastisol is poor, and the coating film has a slightly low strength. In Comparative Example 23, storage stability and coating strength are slightly insufficient. In Comparative Example 24, the storage stability was slightly insufficient, and the coating film strength was greatly reduced.

Comparative Examples 25-26
According to the examples shown in JP-A-53-144950, polymer particles A′25 to A′26 having the compositions shown in Table 1 were produced, and in the same manner as in Example 1, the composition shown in Table 2 was used. A plastisol was prepared. The evaluation results of the plastisol are also shown in Table 2.
Comparative Examples 25 to 26 are cases where the polymer proposed by JP-A-53-144950 is used (A′25 to A′26). In the case of Comparative Example 25, since the compatibility of the polymer with the plasticizer is low, the storage stability is sufficient, but the plasticizer retention is low, bleed out occurs, and the elongation is low. In the case of Comparative Example 26, the compatibility of the core portion was improved, but the methyl methacrylate copolymerization ratio of the shell portion was too high, and the overall compatibility was too low, so the plasticizer retention was low and bleed out occurred.
As described in detail above, the plastisol using the acrylic polymer fine particles of the present invention has excellent storage stability equivalent to a vinyl chloride sol using a vinyl chloride polymer and excellent plasticizer retention, In addition, it is possible to provide a plastisol that does not adversely affect the environment of the vinyl chloride sol, and its industrial significance and the effect on the global environment conservation are remarkable.

Abbreviations in Table 1 are as follows.
MMA: methyl methacrylate nBMA: n-butyl methacrylate iBMA: i-butyl methacrylate MAA: methacrylic acid 2EHA: 2-ethylhexyl acrylate St: styrene EDMA: ethylene glycol dimethacrylate NBMA: N-butoxymethylacrylamide AMA: allyl methacrylate BzMA: benzyl methacrylate CHMA: cyclohexyl methacrylate EMA: ethyl methacrylate AA: acrylic acid nBA: n-butyl acrylate Abbreviations in Table 2 are as follows.
DOP: di-2-ethylhexyl phthalate DINP: diisononyl phthalate DOPh: dioctyl phosphate DBP: butyl benzyl phthalate DEP: diethyl phthalate CaCO ₃ : calcium carbonate The units in the table are as follows.
Formulation: parts by weight Viscosity: Pa · S
Storage stability:%
Strength: MPa
Elongation:%

  The plastisol of the present invention has excellent storage stability, excellent gelation performance, and excellent strength and elongation of the resulting coating film. Various applications such as packing, gaskets, wallpaper and other interior parts, toys, daily necessities, sundries, steel substrate wear and corrosion protection paints, for example, anti-chip coatings on the bottom of automobiles, trucks and buses It can be widely used for forming and coating various coatings such as films, sheets and the like.

Claims (3)

Acrylic polymer fine particles comprising primary particles P having a core-shell structure consisting of a core polymer C and a shell polymer S, wherein the average particle diameter of the primary particles P is 250 nm or more, and the core polymer C and the shell polymer S is a copolymer of the monomer mixture Mc and Ms shown below, respectively, and the acrylic polymer fine particles having a weight ratio of Mc to Ms of 10/90 to 90/10;
Mc: the total is 100 mol%,
Methyl methacrylate 20-85 mol%
(Meth) acrylic acid ester of C2-C8 aliphatic alcohol and / or aromatic alcohol 15-80 mol%, and other copolymerizable monomer 30 mol% or less Ms: the total is 100 mol%,
Methyl methacrylate 20-79.5 mol%
(Meth) acrylic acid ester of C2-C8 aliphatic alcohol and / or aromatic alcohol 5-40 mol%
Carboxyl group or sulfonic acid group-containing monomer
0.5 to 10 mol%, and other copolymerizable monomers 30 mol% or less. The acrylic polymer according to claim 1, wherein the core polymer C and the shell polymer S are copolymers of the monomer mixtures Mc and Ms shown below, respectively, and the weight ratio of Mc and Ms is 30/70 to 70/30. Polymer fine particles;
Mc: the total is 100 mol%,
Methyl methacrylate 20-70 mol%
30 to 80 mol% of one or more (meth) acrylic acid esters selected from the group consisting of n-butyl (meth) acrylate, i-butyl (meth) acrylate and t-butyl (meth) acrylate, and other copolymerizable Monomers 20 mol% or less Ms: the total is 100 mol%,
Methyl methacrylate 30-79.5 mol%
One or more (meth) acrylic acid esters selected from the group consisting of n-butyl (meth) acrylate, i-butyl (meth) acrylate and t-butyl (meth) acrylate 5 to 40 mol%
Carboxyl group-containing acrylic monomer
0.5 to 10 mol%, and other copolymerizable monomers 20 mol% or less. The acrylic polymer according to claim 1, wherein the core polymer C and the shell polymer S are copolymers of the monomer mixtures Mc and Ms shown below, respectively, and the weight ratio of Mc and Ms is 30/70 to 70/30. Polymer fine particles;
Mc: the total is 100 mol%,
Methyl methacrylate 20-70 mol%
30 to 80 mol% of one or more (meth) acrylic acid esters selected from the group consisting of n-butyl (meth) acrylate, i-butyl (meth) acrylate and t-butyl (meth) acrylate, and other copolymerizable Monomers 10 mol% or less Ms: the total is 100 mol%,
Methyl methacrylate 55-79.5 mol%
One or more (meth) acrylic acid esters selected from the group consisting of n-butyl (meth) acrylate, i-butyl (meth) acrylate and t-butyl (meth) acrylate 20 to 40 mol%
Carboxyl group-containing acrylic monomer
0.5-5 mol%, and other copolymerizable monomers 10 mol% or less.