JPS6410004B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for producing composite particles in which a filler is coated with a polymer. "Conventional technology" Conventionally, when blending fillers into thermoplastic resins,
Since the filler is a fine powder, it may generate dust.
There are many problems in mixing and kneading the resin, and due to the influence of particle shape, specific gravity, bulk density, hygroscopicity, particle surface properties, etc., poor dispersion, resin burning due to local heat generation,
Unstable discharge volume, air entrainment, etc. were occurring. As a method to improve these drawbacks, methods have been proposed that mainly use a lubricant or a blended oil in combination with a filler, but these have little effect and, for example, Japanese Patent Publications No. 47-11661 and No. 47-11662 As described in Japanese Patent Publication No. 55-106205, methods of coating fillers with polymers have been proposed, but both require only one step of coating, and furthermore, these inventions Primarily, polymerization initiators that are soluble in the monomers are used. According to these methods, the polymerization of the monomer occurs within the monomer droplets, making it difficult for the polymer to adhere to the surface of the filler, making it impossible to uniformly coat the surface with the polymer, and the surface being not coated with the polymer. Much of the filler itself remained. In addition, even if polymerization is performed using a water-soluble polymerization initiator, the resulting composite particles will be extremely small, similar to the raw material filler, resulting in the generation of dust and the presence of particles in the thermoplastic resin of the filler. The filler was only able to slightly alleviate the non-uniform distribution, etc., and was not a fully satisfactory filler. "Problem to be Solved by the Invention" Based on the descriptions of the above-mentioned known documents, the present inventors have
Furthermore, the composite particles contain a filler that is easy to handle, can be easily filled to a high concentration even when used as a filler, has good dispersibility, and has a satisfactory strength of the resulting molded product. As a result of extensive research, we discovered that a vinyl monomer is polymerized in an aqueous dispersion of the filler in the presence of a water-soluble polymerization initiator to coat the filler, and then the particles of the coated filler are coated with new particles. The present inventors have discovered that the above-mentioned object can be achieved by growing a polymer to have a large particle size, and have completed the present invention. That is, the purpose of the present invention is to increase the particle size of the filler and increase its bulk specific gravity, improve the handling workability and dispersibility of the filler, and improve the physical properties of the resulting molded product. It is an object of the present invention to provide a method for producing composite particles containing fillers. "Means for Solving the Problems" The gist of the present invention is to add a vinyl monomer and a water-soluble polymerization initiator to an aqueous dispersion in which a filler is uniformly dispersed in water. The vinyl monomer is radically polymerized to form a thin film of the polymer on the surface of the filler, and after the radical polymerization is completed, the excess water-soluble polymerization initiator remaining in the polymerization system is decomposed to form an aqueous dispersion. a first step of producing a polymer-coated filler, and then a vinyl monomer is further added to the aqueous dispersion of the polymer-coated filler produced in the first step; The vinyl monomer is polymerized by a suspension polymerization method in the presence of an oil-soluble polymerization initiator soluble in A method for producing composite particles comprising two steps. The present invention will be explained in detail below. The first step in the present invention is to add a vinyl monomer and a water-soluble polymerization initiator to an aqueous dispersion in which a filler is uniformly dispersed in water, and to radically polymerize the vinyl monomer in water. By forming a thin polymer film on the surface of the filler, and then decomposing the excess water-soluble polymerization initiator remaining in the polymerization system after radical polymerization, a polymer-coated filler is produced as an aqueous dispersion. It refers to the process of In the present invention, fillers are not particularly limited as long as they are fillers used for thermoplastic resins, and specifically include silica, mica, talc, stone powder, diatomaceous earth, clay, volcanic ash, and coal ash. , bentonite, graphite, carbon black, calcium carbonate, calcium sulfate, calcium sulfite, titanium oxide, zinc white, alumina, antimony trioxide, aluminum powder, copper powder, iron powder, molybdenum disulfide, barium sulfate, polyallylurea, copper Examples include phthalocyanine, wood powder, asbestos powder, glass powder, etc., and at least one of these is used. These fillers may be used after the surface thereof has been previously treated with a silane coupling agent, a titanate coupling agent, a fatty acid, or the like. However, the average particle size of these fillers is
A particle size in the range of 0.01 to 100 μm, especially 0.1 to 20 μm is preferable. If the average particle size is smaller than 0.01 μm, the surface area of the filler and apparent voids are large, so the amount of vinyl monomer used in the first step is large. , it becomes difficult to produce composite particles containing a high concentration of filler, and if the size exceeds 100 μm, the desired physical properties of the composite cannot be obtained, so the advantage of producing composite particles decreases. . Vinyl monomers used in the present invention include ethylene, propylene, butylene, 4-methylpentene-1, vinyl chloride, vinyl fluoride, vinyl bromide, vinyl acetate, vinyl propionate, vinyl stearate, vinyl methyl ether, vinyl ethyl Ether, vinyl isobutyl ether, vinyl phenyl ether, acrylic acid, methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, styrene, vinyltoluene, methoxystyrene, divinylbenzene, chlorstyrene,
Dichlorostyrene, α-vinylnaphthalene, acrylonitrile, vinyl methyl ketone, vinyl pyridine, vinylidene chloride, vinylidene fluoride, isobutylene, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid-2-
Ethylhexyl, α-methylstyrene, 1,1-
Examples include chlorofluorinated ethylene. Furthermore, the present invention is not limited to these examples, and they may be used alone or as a mixture of two or more. Ethylene, propylene, etc. are uneconomical because they require high pressure to liquefy and require extremely strong pressure-resistant containers, so they are often used as comonomers. The vinyl monomer used in the first step is
Among the above-mentioned monomers, it is preferable to select a monomer that has a particular affinity with the filler particles. According to this selection criterion, the optimal vinyl monomer is, for example, when talc, silica, calcium carbonate, etc. are selected as fillers; unsaturated acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid; Various esters of alcohols having 10 or fewer carbon atoms, glycols having 4 or fewer carbon atoms, or oligomers of ether glycols having 10 or less carbon atoms, alkyl-substituted amino alcohols, glycidyl alcohols, etc., and acrylic acid, methacrylic acid, maleic acid, etc.; acetic acid Vinyl; p-styrenesulfonic acid; vinylpyridine; acrylamide; acrylonitrile and the like are preferred, specifically butyl acrylate,
Methyl methacrylate, allyl methacrylate,
Glycidyl methacrylate, isopropyl maleate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and the like are preferred. Therefore, the amount of vinyl monomer used in the first step depends on various conditions, such as the size and shape of the filler particles, and the affinity with the new polymer produced by polymerization in the second step, which will be described later. It depends on the amount of vinyl monomer per 100 parts by weight of filler.
It is preferable to select the amount in the range of 0.5 to 100 parts by weight, preferably 2 to 30 parts by weight. The water-soluble polymerization initiator used in the first step of the present invention is one that dissolves in water or by heating, and generates radicals in water or by heating in water, or in the presence of an auxiliary agent in water. However, there are no particular limitations as long as the above-mentioned vinyl monomer can be radically polymerized. For example, hydrogen peroxide; persulfates such as ammonium persulfate, potassium persulfate, sodium persulfate, etc.; hydroperoxides such as p-menthane hydroperoxide; percarboxylic acids such as peracetic acid; Oxymaleic acid; 2-cyano-2-propylazoformamide; acetyl peroxide, etc., which may be used alone or in combination with two
Can be used in combination with more than one species. Of course, a polymerization initiation aid such as a ferrous salt, acidic sodium sulfite, or ascorbic acid may be used in combination with these water-soluble polymerization initiators. The amount of water-soluble polymerization initiator used varies depending on the type and amount of filler and vinyl monomer used, but usually the water-soluble polymerization initiator is used per 100 parts by weight of the vinyl monomer used in the first step. 0.01~100
It is preferably selected in parts by weight, particularly in the range of 0.1 to 10 parts by weight. The reason why the amount of water-soluble polymerization initiator used is wide is that some fillers react with the initiator as a radical catcher and consume it. It is desirable to determine the amount of polymerization initiator. In the first step of the present invention, in the polymerization reaction tank, first,
Disperse the filler in water. Normal stirring is sufficient to uniformly disperse the filler in water, but if the filler particles have been hydrophobically treated or are fine, use a homomixer etc. to sufficiently disperse them to prevent secondary aggregation. It is necessary to prevent this from occurring and to disperse it uniformly in the water. However, if stirring is stopped, the filler may separate and settle, so it is preferable to stir continuously. Continuous stirring is sufficient for dispersing the filler, but if necessary, an emulsifier may be added as a dispersion aid. However, if too much emulsifier is used, it tends to inhibit the adhesion of the polymer to the filler, so it is preferable to strictly select the type and amount of emulsifier, or rather not use it. At this time, the emulsifiers used include emulsifiers used in normal emulsion polymerization, such as anionic surfactants such as lauryl alcohol sulfate and alkyl sulfonates, and nonionic surfactants such as esters of polyethylene oxide and fatty acids. Examples include drugs. After uniformly dispersing the filler in water, vinyl monomer is added to the water, the inside of the reaction tank is replaced with an inert gas such as nitrogen gas, and a water-soluble polymerization initiator is injected.
The vinyl monomer is radically polymerized while stirring.
The particles of the polymerized polymer are extremely small, and as the polymerization reaction progresses, they adhere to the filler through a reaction such as grafting or adsorption, forming a thin film of the polymer on the surface of the filler. The vinyl monomer and the water-soluble polymerization initiator may be added in their entirety into the reaction tank from the initial stage of polymerization, or may be added continuously or intermittently as the polymerization reaction progresses. The first step of radical polymerization of a vinyl monomer using a water-soluble polymerization initiator can be carried out by a method similar to a normal emulsion polymerization method, and a filler coated with a polymer is produced by this step. Ru. The particle size of the polymer-coated filler varies depending on the amount of monomer used, but is slightly larger than the particle size of the filler used. After the vinyl monomer undergoes radical polymerization and substantially disappears from the polymerization system, that is, after the radical polymerization is completed, the excess water-soluble polymerization initiator remaining in the polymerization system is removed in advance before proceeding to the second step. It is necessary to decompose it using heat or a decomposing agent.
If the water-soluble polymerization initiator remains in the polymerization system, it will undergo a polymerization reaction with the added vinyl monomer in the second step to be described later, producing emulsified fine particles, which is undesirable because the recovery rate of the resulting composite particles will decrease. . In the second step of the present invention, following the first step, a vinyl monomer is further added to the aqueous dispersion of the polymer-coated filler produced in the first step, and a vinyl monomer is added to the aqueous dispersion of the polymer-coated filler produced in the first step. This is a process in which the vinyl monomer is polymerized by a suspension polymerization method in the presence of an oil-soluble polymerization initiator, and the polymer-coated filler is coated with a new polymer to increase the particle size. The desired composite particles are obtained through the second step. In this second step, the particles of the polymer-coated filler produced in the first step are coated with a new polymer of vinyl monomer, and the particles of the coated filler are agglomerated and enlarged to have a large particle size. It is characterized by becoming The vinyl monomer used in the second step may be the same as the vinyl monomer listed above.
The vinyl monomer used in the second step is preferably selected appropriately depending on the purpose of use of the finally obtained composite particles. Among them, it is compatible or has affinity with the skin polymer of the polymer-coated filler obtained in the first step, and when the composite particles are used as an additive for a thermoplastic resin, the compatibility with the resin is It is preferable to use a vinyl monomer from which a good polymer can be obtained. The amount of the vinyl monomer used in the second step is preferably in the range of 5 to 500 parts by weight per 100 parts by weight of the filler used in the first step. Particularly preferred is a range of 10 to 100 parts by weight. Examples of the oil-soluble polymerization initiator soluble in the vinyl monomer used in the second step include lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, t-butylperoxypivalate, diisopropylperoxy dicarbonate, 2-ethylhexyl peroxycarbonate, sec-butyl peroxydicarbonate,
Organic peroxides such as acetylcyclohexylsulfonyl peroxide or 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-
Examples include azo compounds such as dimethylvaleronitrile, which are used alone or in combination of two or more. The amount of the oil-soluble polymerization initiator soluble in the vinyl monomer can be selected within the range of 0.05 to 20 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the vinyl monomer added in the second step. . In the suspension polymerization in the second step, a suspending agent can be added to the polymerization system as necessary. Specific examples of suspending agents include partially saponified polyvinyl acetate, gelatin, methylcellulose, polyacrylic acid, polyvinylpyrrolidone, vinyl acetate-maleic acid copolymer, and dodecylbenzenesulfone as necessary. Examples include the use of one or more emulsifiers such as sodium acid, sodium lauryl sulfate, sodium laurate, sorbitan monolaurate, polyoxyethylene nonyl phenyl ether, or a combination of two or more suspending agents. In the second step of the present invention, a desired amount of at least one vinyl monomer from which a desired new polymer is produced is added to the aqueous dispersion of the polymer-coated filler produced in the first step. If necessary, a suspending agent is used in combination to carry out suspension polymerization in the presence of an oil-soluble polymerization initiator soluble in the vinyl monomer, and the filler is increased in size to form composite particles. Manufacture. Various known aqueous suspension polymerization techniques can be applied to the granulation step in this second step. The composite particles obtained by the method of the present invention are directly used as a molding material as a filler-containing thermoplastic resin, and are subjected to various molding processes such as extrusion molding, injection molding, rotary molding, inflation molding, press molding, and calender roll processing. It can be used in any method. Furthermore, the composite particles obtained by the method of the present invention can be used as an additive for thermoplastic resins such as ABS resins, vinyl chloride resins, HIPS, and polyolefins. At the time of addition and mixing, there is no dusting, measurement is easy, and the filler can be contained in the thermoplastic resin at a high concentration. "Effects of the Invention" The present invention has been described above, and has particularly remarkable effects as described below, and its industrial utility value is extremely large. (1) When using the method of the present invention, since the composite particles are manufactured in an aqueous dispersion, there is no generation of dust due to fine powder of the filler, and the work environment in which the composite particles are manufactured is not contaminated. (2) According to the method of the present invention, it is possible to produce composite particles that have a larger particle size and bulk specific gravity than the raw material filler, are superior in handling workability, and contain a high concentration of filler. I can do it. (3) Composite particles produced by the method of the present invention,
When used as a molding material as it is, it exhibits good molding processability and the resulting molded product also has excellent physical properties. (4) Composite particles produced by the method of the present invention,
When used in addition to another thermoplastic resin, the composite particles exhibit excellent dispersibility, affinity, and compatibility with the other thermoplastic resin. "Examples" Next, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1, Comparative Example 1 2000 g of deionized water and 800 g of talc having an average particle size of 10 μm were placed in a four-necked glass flask with an internal volume of 3 I and equipped with a stirrer, and the flasks were thoroughly stirred and dispersed. After adding 40 g of the vinyl monomer shown in Table 1 into the flask, the inside of the system was purged with nitrogen gas and the internal temperature was raised to 70°C. Next, add 1g of potassium persulfate and
The temperature was maintained at 90°C for 1.5 hours, and then the temperature was raised to 90°C. The reaction was carried out at that temperature for 1 hour to decompose the remaining potassium persulfate, completing the first step of producing the polymer-coated filler. Next, the internal temperature was lowered to 80℃ and the styrene was heated.
128g, acrylonitrile 52g, terpinolene 1g,
5 g of benzoyl peroxide and 1 g of azobisisobutyronitrile were added, and polymerization was carried out at 80° C. for 2 hours. The internal temperature of the flask was raised to 90°C, and unreacted monomers were distilled off by stripping for 1 hour under nitrogen gas flow to complete the second step. Thereafter, the resulting aqueous dispersion was separated through a 200-mesh (Taylor sieve) wire mesh, washed, and dried to obtain composite particles. The respective yields were as shown in Table 1. The liquid was clear and colorless. The talc content of the composite particles was 80% by weight. For comparison, in the example described in Example 1, the polymerization in the first step was not performed, and the amount of monomers added in the second step was changed to 160 g of styrene and 60 g of acrylonitrile, but the second step of the same example was performed. Perform only the polymerization operation corresponding to the second step under the same conditions,
Composite particles were obtained. The liquid was cloudy, and floating particles of filler whose surface was not coated with polymer were observed.

[Forming method A]

A method in which the composite particles are molded into a flat plate using a hot press molding method at 185°C for 20 minutes, and a test piece is created from this flat plate. [Forming method B] A predetermined weight part of the composite particles is mixed with 100 parts by weight of vinyl chloride resin with a degree of polymerization of 1050, 4 parts by weight of basic lead sulfate,
After mixing with 0.3 part of lead stearate in a mixer, kneading it into a gel at 180℃ for 5 minutes with two rolls,
A method in which a flat plate is then formed by press molding at 185°C for 5 minutes, and a test piece is created from this flat plate.

[Table] In Ratio-1, when the same molding operation as 1-a was performed, the sample was a fine powder and had a small bulk specific gravity, so it could not be degassed and a flat plate could not be formed by the press molding method. By mixing the composite particles of Example 1-No. 1 with vinyl chloride resin as an additive, the dispersibility on the two mixing rolls was improved compared to when the filler was mixed as it was, that is, when the raw filler was mixed. It has a fast gelation time, good persistence of lubricity, no fluctuation in gelation and lubricity depending on the amount of lubricant, and a slow dispersion rate when heated. In particular, composite particles obtained by the method of the present invention blended with hard vinyl chloride resin exhibit the following various effects compared to those in which filler powder is simply added. ``Effects in terms of operation and processing'' 1. Ease of handling (no dusting or adhesion to vessel walls) 2. Improved processability (1) Quick gelation. (2) Smoothness is moderate and durable. (3) Good dispersion of filler. (a) Good reproducibility of physical properties. (b) Less heat generation and pressure increase in the extruder;
Biting and discharge amount are stable. 3 Appearance of molded product (1) No air entrapment. (2) A smooth surface can be obtained. (3) Good thermal stability and little discoloration. "Effects in terms of physical properties" 1 Improvement in bending strength 2 Improvement in rigidity 3 Improvement in heat resistance 4 Improvement in creep properties 5 Improvement in heat deformation temperature 25 parts by weight of the composite particles of .1 were added and injection molded, and a test sample was taken from the molded product and its physical properties were measured and are listed in Table 3. For comparison, the composite particles obtained in Comparative Example 1 were also tested in the same manner.

【table】

[Table] In the examples shown in Table 3, the composite particles obtained by the method of the present invention were easily bited into the injection molding machine, and no air was trapped. On the other hand, in the case of using the particles obtained in Comparative Example 1, although the penetration into the injection molding machine was improved compared to conventional fillers, it was still not sufficient and there was a lot of dust.
This is reflected in the physical properties in Table 3. Example 2, Comparative Example 2 Using the same equipment as Example 1, 2000 g of deionized water
After thoroughly mixing and dispersing 600 g of talc with an average particle size of 3 μm, 50 g of acrylic acid and 100 g of n-butyl acrylate were added, and the internal temperature was brought to 60°C. Add 1.2g of potassium persulfate and hold at 65℃ for 1.5 hours, then
The temperature was raised to 90°C. The reaction was carried out at 90° C. for 1 hour to produce a polymer-coated filler. After completing this first step, the aqueous dispersion was brought to an internal temperature of 80°C, 280 g of styrene, 160 g of acrylonitrile, 1.6 g of benzoyl peroxide, and 0.2 g of terpinolene.
Mix and dissolve and add, react at 80℃ for 2 hours, and then heat to 90℃.
Stripping was carried out for 1 hour, followed by post-treatment in the same manner as in Example 1 to obtain composite particles. The average particle size was 523 μm. The liquid was also colorless and transparent. For comparison, in the example described in Example 2, the first step was omitted and styrene was added in the second step.
Composite particles were produced by performing only the polymerization operation corresponding to the second step under the same conditions as in the second step of the same example except that 420 g of acrylonitrile and 200 g of acrylonitrile were used. The average particle size of the composite particles was 68 μm, and the composite particle separated liquid was extremely cloudy. These composite particles were molded into a flat plate by hot press molding at 185°C for 20 minutes, test pieces were made from this flat plate, and mechanical properties were measured. The results are shown in Table 4.

[Table] Example 3 In the example described in Example 1-No.
In place of 800 g of fatty acid-treated calcium carbonate having an average particle size of 0.1 μm or less, and after adding a vinyl monomer in the second step, 5 minutes later, 10 g of a 2% by weight aqueous solution of partially saponified polyvinyl acetate was added as a suspending agent. Except for the addition, composite particles were produced in the same manner as in the same example. The average particle size of the particles is 913 μm
was growing up. Example 4 Into the same flask used in Example 1, 2000 g of deionized water was charged, and 104 g of hydrated silica of 0.1 μm or less was well dispersed therein, and 8 g of dimethylaminoethyl methacrylate and 10 g of butyl acrylate were added.
was added and the temperature was raised to 70°C. Add 1 g of potassium persulfate and polymerize at 70°C for 1 hour 20 minutes, then add 2 g of dimethylaminoethyl methacrylate, 79 g of 2-ethylhexyl acrylate and 1 g of ethylene glycol dimethacrylate, polymerize at 70°C for 40 minutes, then add potassium persulfate. Added 1g. The temperature was raised and maintained at 80°C for 2 hours, followed by reaction at 90°C for 1 hour to produce an aqueous dispersion of the polymer-coated filler. As the second step, after cooling down to 80℃, styrene
234g, acrylonitrile 86g, benzoyl peroxide 1.2g, azobisisobutyronitrile 0.4g
and 0.4 g of terpinolene were added, and after 2 minutes,
A 2% aqueous solution of partially saponified polyvinyl acetate was added as a suspending agent, polymerization was performed at 80°C for 2 hours, and stripping was performed at 90°C for 1 hour to produce composite particles.
The average particle diameter was 848 μm, and the composite particle separation liquid was clear and colorless.

Claims (1)

[Claims] 1. A vinyl monomer and a water-soluble polymerization initiator are added to an aqueous dispersion in which a filler is uniformly dispersed in water, and the vinyl monomer is radically polymerized in water to form a filling material. By forming a thin film of polymer on the surface of the material,
Next, after the radical polymerization is completed, a first step of producing a polymer-coated filler in the form of an aqueous dispersion by decomposing the excess water-soluble polymerization initiator remaining in the polymerization system; A vinyl monomer is further added to the aqueous dispersion of the polymer-coated filler prepared above, and the vinyl monomer is polymerized by suspension polymerization in the presence of an oil-soluble polymerization initiator soluble in the vinyl monomer. A method for producing composite particles, comprising: a second step of polymerizing the polymer-coated filler and enlarging the particle size by coating the polymer-coated filler with a new polymer.