JP3409363B2 - Method for producing silica-containing acrylic polymer composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silica-containing acrylic polymer composition. More specifically, the present invention relates to a method for producing an acrylic polymer composition containing silica using a silane coupling agent. In order to compound silica with an acrylic polymer, it is necessary to use a kneader such as a roll or a kneader to put the polymer and silica into a kneader, to mix and knead them. Is being done. At this time, a silane coupling agent is used in combination for the purpose of improving the physical properties of the obtained acrylic polymer composition, particularly the compression set resistance. The silane coupling agent is added to the kneader or added together with silane from the beginning, but when the acrylic polymer, silica, and silane coupling agent are mixed in the kneader, shearing occurs. The mixing temperature rises due to heat generation and friction with the vessel wall, and the volatilization of the silane coupling agent cannot be avoided. Further, only a composition in a poorly dispersed state can be obtained. [0003] For this reason, it is possible to avoid variations within and between batches, for example, the mixing amount of the silane coupling agent varies for each kneading batch, and sometimes silica not treated with the silane coupling agent occurs. Without
Variations also occur in physical properties. SUMMARY OF THE INVENTION An object of the present invention is to provide an acrylic polymer composition containing silica by using a silane coupling agent in combination with an acrylic polymer, which has a high compression set. An object of the present invention is to provide a material having excellent properties and a good dispersion state of silica. [0005] The object of the present invention is to provide
(a) at least one of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate and (b) epoxy
Vinyl monomer containing carboxyl group, vinyl monomer containing carboxyl group
, Reactive halogen-containing vinyl monomer, diene monomer
Or a cure site monomers are hydroxyl group-containing vinyl monomer is emulsion polymerization or suspension polymerization at 50 to 90 ° C., form there
Silica pre-heated to 50-90 ° C in the formed polymerization solution
Add the silane coupling agent aqueous dispersion and add 50-90
This is achieved by producing a silica-containing acrylic polymer composition characterized by continuing stirring at a temperature of ° C. The alkyl (meth) acrylate of the component (a) includes, for example, methyl acrylate, ethyl acrylate, n- or iso-propyl acrylate, n- or iso-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, -Ethylhexyl acrylate,
n-octyl acrylate, an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms (including those having a substituent such as a cyano group) such as 2-cyanoethyl acrylate or a corresponding alkyl methacrylate is used, and preferably ethyl acrylate Alternatively, n-butyl acrylate or methyl methacrylate, ethyl methacrylate or n-butyl methacrylate is used. The alkoxyalkyl (meth) acrylates include, for example, those having 2 to 2 carbon atoms such as methoxymethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate or the corresponding methacrylate. An alkoxyalkyl (meth) acrylate having an alkoxyalkyl group of 8 is used, preferably 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate or the corresponding methacrylate. The component (a) is used as a main component of the acrylic copolymer in a proportion of about 90 to 50% by weight, preferably about 90 to 60% by weight, and contains an alkyl (meth) acrylate and an alkoxyalkyl ( When both (meth) acrylates are used, the former is about 90 to 10 mol%, and the latter is about 10 to 10 mol%.
It is generally used in a proportion of ~ 90 mol%. A part of the component (a), specifically, up to about 30% by weight, may be replaced with another copolymerizable monomer and copolymerized. Examples of such a copolymerizable monomer include ethylene, propylene, vinyl chloride, vinylidene chloride, acrylonitrile, styrene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, alkyl methacrylate, and alkoxyalkyl methacrylate. As the component (b) for forming a crosslinking point of the copolymer, the following can be used. (A) Epoxy group-containing vinyl monomers such as allyl glycidyl ether, glycidyl vinyl ether, glycidyl acrylate and glycidyl methacrylate. (B) Carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, itaconic acid and maleic acid monoester. (C) Reactive halogen-containing vinyl monomers such as 2-chloroethyl vinyl ether, 2-chloroethyl acrylate and monochlorovinyl acetate. (D) diene monomer isoprene, pentadiene, vinylcyclohexene, chloroprene, butadiene, methylbutadiene, cyclopentadiene, methylpentadiene, ethylidene norbornene, vinylidene norbornene, allyl acrylate,
Examples thereof include 2-butenyl acrylate, dihydroethylidene norbornenyl acrylate, and dihydrodicyclopentadienyl acrylate. (E) Hydroxyl group-containing vinyl monomers such as hydroxyalkyl acrylate, hydroxyalkyl methacrylate, hydroxyalkoxy acrylate, and N-methylol acrylamide. The copolymerization reaction is carried out by an emulsion polymerization method or a suspension polymerization method in the presence of a radical polymerization initiator. As the radical polymerization initiator, generally used organic peroxides, azo compounds, inorganic persulfates and the like are preferably used as a redox system, and together therewith, a chain transfer agent such as an organic mercapto compound and an organic sulfide compound is also used. Used. When a predetermined degree of polymerization is reached by the polymerization reaction, an aqueous dispersion of a silica / silane coupling agent is added. The point of addition can be determined by previously obtaining the correlation between the molecular weight of the obtained copolymer, the stirring torque, the micelle particle size, and the like. As the silica used for preparing the aqueous dispersion of the silica-silane coupling agent, either dry silica or wet silica can be used. As the silane coupling agent, an epoxy group, preferably an organic reactive group, Those having a mercapto group or the like, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane and the like are used. Silica is generally an acrylic copolymer 100
It is used in a ratio of about 5 to 40 parts by weight, preferably about 10 to 25 parts by weight per part by weight. Also, in order to attach the silane coupling agent to all silica in a monomolecular film,
A minimum amount (g) calculated by the following formula is required, and it is generally used in a proportion of about 0.1 to 25 parts by weight, preferably about 2 to 20 parts by weight, per 100 parts by weight of the acrylic polymer. Silica weight (g) × silica specific surface area (m ² / g) / minimum coverage area of silane coupling agent (m ² / g) The silane coupling agent hydrolyzes when added to water, Silane coupling agent prepared by a method of dispersing silica in water and then adding a silane coupling agent or a method of adding silica and dispersing silica after adding water Used as an aqueous dispersion. Silane coupling agents are easier to hydrolyze at lower pH,
The silane coupling agent is more easily hydrolyzed because the pH is lowered only by adding silica. However, if necessary, the pH may be adjusted by adding an acid such as acetic acid. In the prepared aqueous dispersion of the silica-silane coupling agent, the silane coupling agent is efficiently bonded to the silica surface, and the silica is in a good dispersion state in the aqueous dispersion. When added to the solution, an acrylic polymer composition in which the silane is well dispersed is formed.
The addition of the aqueous dispersion is preferably performed after heating to that temperature in advance according to the polymerization temperature generally performed at about 50 to 90 ° C., and after the addition, the mixture is further stirred at that temperature for about 10 to 60 minutes, It is separated as a composition by salting out. In the obtained silica-containing acrylic polymer composition, a crosslinking agent corresponding to the type of the crosslinkable group copolymerized in the acrylic polymer, for example, when the crosslinkable group is a reactive halogen group, Polyamine, polyamine salt, fatty acid alkali metal salt and sulfur or sulfur donor compound, trithiocyanuric acid and fatty acid metal salt, dicyandiamide, metal oxide, dithiocarbamate or thiuram compound and the like cross-linking agent and other necessary compounding agents Vulcanization is carried out by primary vulcanization at about 150-210 ° C. for about 0.5-15 minutes and optional secondary vulcanization at about 120-180 ° C. for about 1-20 hours. According to the method of the present invention, an acryl-based polymer composition in which a silane coupling agent is efficiently bonded to a silica surface and silane is well dispersed is obtained. Also excellent in compression set. Next, the present invention will be described by way of examples. EXAMPLE 1 Ethyl acrylate 480 g 2-chloroethyl vinyl ether 20 n-sodium dodecyl sulfate 10 sodium hydrogen sulfite 0.0125 ammonium persulfate 0.0125 octyl mercaptan 0.1 A mixture of water 1000 was heated at 60 ° C. for 3 hours, corresponding to a molecular weight of 400,000. A polymerization solution in which a copolymer was formed was obtained. To the polymerization solution (60 ° C.), an aqueous dispersion of the silica / silane coupling agent prepared by the method described below is added after heating to 60 ° C., and stirring is further continued for 30 minutes to obtain a molecular weight of 450,000. A polymerization solution in which a copolymer was formed was obtained. 400 g of sodium chloride was added to the polymerization solution, and the salted-out composition was washed three times with water, and then dried at 80 ° C. for 8 hours. When a freeze-cut surface of the obtained composition (448 g) by an ultramicrotome was observed by SEM, no aggregate of silica was observed. (Preparation of aqueous dispersion of silica-silane coupling agent) 400 g of water
To silane coupling agents (Shin-Etsu Silicone KBM
403; γ-glycidoxypropyltrimethoxysilane) 20 g
And 40 g of silica (Aerosil # 200) were added and stirred.
Before adding silica, the concentration of methanol produced by hydrolysis of the silane coupling agent in the liquid was determined by liquid chromatography to obtain a value of 1 × 10 ^-3 mol / g. Was found to be hydrolyzed. In addition, the solution after adding silica is filtered,
When the silane coupling agent in the solution was quantified by liquid chromatography, a value of 3.9 × 10 ^-4 mol / g was obtained.
It was found that 91% of the hydrolyzed silane coupling agent bound to silica (70% bound to silica for the silane coupling agent used). Comparative Example 1 The mixture of Example 1 was heated at 60 ° C. for 3.5 hours to obtain a polymerization solution in which a copolymer having a molecular weight of 450,000 was formed, and 300 g of sodium chloride was added thereto, followed by salting out. Washing and drying were performed in the same manner. To 400 g of the obtained 408 g of the copolymer, 40 g of silica (Aerosil # 200) was kneaded with an 8-inch roll for 10 minutes, and then 20 g of a silane coupling agent (KBM403) was added.
Kneaded for minutes. At this time, an irritating gas was generated, and some volatilization of the silane coupling agent was recognized. About this composition, the frozen cut surface by the ultra microtome is
Observation by SEM revealed the presence of many aggregates. Example 2 n-Butyl acrylate 480 g Vinyl chloroacetate 20 n-Dodecyl sodium sulfate 10 Sodium bisulfite 0.0125 Ammonium persulfate 0.0125 Octyl mercaptan 0.1 A mixture of water 1000 was heated at 62 ° C. for 2.5 hours, corresponding to a molecular weight of 380,000. A polymerization solution in which a copolymer was formed was obtained. To this polymerization solution (62 ° C.), 350 g of water, 20 g of a silane coupling agent (Shin-Etsu Silicone Product KBM803; γ-mercaptopropyltrimethoxysilane) and 68 g of silica (Aerosil # 200) were prepared by the above method. The obtained aqueous dispersion of the silica-silane coupling agent was heated to 62 ° C., added thereto, and further stirred for 30 minutes to obtain a polymerization solution in which a copolymer having a molecular weight of 420,000 was formed. 380 g of sodium chloride was added to the polymerization solution, and the salted-out composition was washed three times with water, and then dried at 80 ° C. for 8 hours. The resulting composition (50
When the frozen cut surface of the 3g) ultramicrotome was observed by SEM, no aggregate of silica was observed. Comparative Example 2 The mixture of Example 2 was heated at 62 ° C. for 3 hours to obtain a polymerization solution in which a copolymer having a molecular weight of 420,000 was formed. Washing and drying were performed in the same manner. To 400 g of the obtained 425 g of the copolymer, 68 g of silica (Aerosil # 200) was kneaded with an 8-inch roll for 10 minutes, and then 20 g of a silane coupling agent (KBM803) was added.
Kneaded for 5 minutes. At this time, an irritating gas was generated, and some volatilization of the silane coupling agent was recognized. When the frozen cut surface of this composition was cut with an ultramicrotome by SEM, the presence of many aggregates was observed. Various vulcanizing ingredients were added to 100 parts by weight of the compositions obtained in the above Examples and Comparative Examples, kneaded, and then press vulcanized at 200 ° C. for 2 minutes. The normal value of the obtained vulcanized sheet was measured, and the result was shown in the following table together with the amount of the vulcanizing compounding agent. Table 1 Comparative Example 1 Comparative Example 2 Comparative Example 2 [Vulcanizing compounding agent: parts by weight] Diamond black H 15 15 15 15 Celite SF 20 20 15 15 Stearic acid 1 1 1 1 Calcium hydroxide 1 1 1 1 Sulfur 0.4 0.4 0.3 0.3 Stearic acid Na 3 3 3.5 3.5 Stearic acid K 1.5 1.5 1.2 1.2 [Normal value] Hardness (JIS A) 71 67 72 69 100% modulus (MPa) 6.1 5.7 6.3 5.8 Tensile strength (MPa) 6.5 6.2 6.6 6.3 Elongation at break (%) 131 138 125 129 Compression set (%) 56 65 67 71

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C08K 3/36 C08K 3/36 5/541 C08L 33/06 C08L 33/06 C08K 5/54 (58) Fields surveyed (Int. Cl ^7, DB name) C08F 220/00 -. 220/70 C08F 6/00 - 6/28 C08F 8/00 - 8/50 C08J 3/00 - 3/28 C08L 33/00 - 33/26

Claims (1)

(57) [Claims] (1) At least one of (a) an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, and (b) an epoxy group-containing vinyl monomer, a carboxyl group
Containing vinyl monomer, reactive halogen-containing vinyl monomer,
Emulsion polymerization or suspension polymerization of a diene monomer or a crosslinking monomer which is a hydroxyl group-containing vinyl monomer at 50 to 90 ° C. is performed, and the polymerization solution formed there is previously added to the polymerization solution at 50 to 90 ° C. Heated to
Adding silica-silane coupling agent aqueous dispersions
A method of producing a silica-containing acrylic polymer composition , wherein stirring is further continued at 50 to 90 ° C.