JP2006299104A - Thermoplastic resin composition and molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition which has the original characteristics of a polyacetal resin, can obtain a molded article whose mechanical properties especially such as impact resistance or the like are improved and in which decomposition of a polyacetal resin is suppressed, and to provide the molded article. <P>SOLUTION: The thermoplastic resin composition comprises: a graft copolymer (A) obtained by carrying out the graft polymerization of a vinyl monomer with a rubbery polymer (R) obtained by carrying out the polymerization of a monomer which composes the rubbery polymer under the presence of a surfactant derived from a gum rosin or a surfactant derived from an N-acylamino acid; and a polyacetal resin (B). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermoplastic resin composition containing a polyacetal resin and a molded article formed by molding the same.

  Polyacetal resin is an engineering plastic with excellent mechanical strength, fatigue resistance, slidability, chemical resistance, etc., made of resin in OA equipment, information equipment, home appliances, automobiles, clothing, stationery, sundries, building materials, etc. Widely used as materials for gears, mechanical parts, etc. In particular, in addition to the above characteristics, it can be mass-produced at low cost, etc., so that it is used as a material for buttons, clips, and gears that require the above characteristics.

When polyacetal resin is used as a material for buttons, clips, and gears, performance such as high impact resistance, low noise, low wear, and high accuracy is required. In particular, it is important to have excellent impact resistance.
As a means for improving the impact resistance of a molded article made of polyacetal resin, a reinforcing filler such as an inorganic filler such as glass fiber, carbon fiber, potassium titanate whisker, calcium carbonate, or talc is added to polyacetal resin. It is possible. However, since the reinforcing filler is usually harder than the polyacetal resin, the reinforcing filler may scrape the polyacetal resin during sliding to increase the amount of wear.

In addition, homopolymers and copolymers exist in polyacetal resins, and homopolymers tend to have higher impact resistance than copolymers. However, the homopolymer has a large post-shrinkage accompanying the progress of crystallization, and therefore has poor dimensional stability and is not suitable for the exemplified applications.
In addition, in consideration of plating applications, clip characteristics, and the like, Patent Document 1 and Examples in which a core-shell polymer having a rubber-like polymer core and a glass-like polymer shell is blended with a polyacetal resin to improve impact resistance are disclosed. 2 is proposed. However, the impact resistance is still insufficient, and further improvement in impact resistance is required. Further, there is a problem that the polyacetal resin is easily decomposed during melt-kneading and molding of the core-shell polymer and the polyacetal resin.
JP-A-2-129266 JP-A-6-1000075

  An object of the present invention is to provide a thermoplastic resin composition having inherent properties of a polyacetal resin, particularly capable of obtaining a molded article having improved mechanical properties such as impact resistance, and in which decomposition of the polyacetal resin is suppressed, and An object of the present invention is to provide a molded article having the original characteristics of polyacetal resin and having improved mechanical properties such as impact resistance.

The thermoplastic resin composition of the present invention contains a graft copolymer (A) obtained by graft polymerization of a vinyl monomer to a rubbery polymer (R), and a polyacetal resin (B). The rubbery polymer (R) is obtained by polymerizing monomers constituting the rubbery polymer in the presence of a surfactant derived from gum rosin or a surfactant derived from N-acylamino acid. It is characterized by the above.
The molded article of the present invention is formed by molding the thermoplastic resin composition of the present invention.

According to the thermoplastic resin composition of the present invention, it is possible to obtain a molded product having the original characteristics of a polyacetal resin, in particular, improved mechanical properties such as impact resistance, and the decomposition of the polyacetal resin is suppressed.
The molded article of the present invention has the original characteristics of polyacetal resin, and particularly has improved mechanical properties such as impact resistance.

<Rubber polymer (R)>
The rubber polymer (R) is obtained by polymerizing monomers constituting the rubber polymer in the presence of a surfactant derived from gum rosin or a surfactant derived from N-acylamino acid. It is a thing.
Various polymerization methods can be used for the production of the rubbery polymer (R), and an emulsion polymerization method is preferred.

  By using a surfactant derived from gum rosin or a surfactant derived from N-acylamino acid, compared to the case of using a saturated or unsaturated fatty acid surfactant used in ordinary emulsion polymerization, etc. The stability of the polyacetal resin (B) can be improved. In the case of a surfactant derived from gum rosin, the main component thereof is abithienoic acid. In the case of a surfactant derived from N-acylamino acid, the structure of the acylamino group part contributes to stabilization. It is estimated to be.

Examples of the surfactant derived from gum rosin include gum rosin potassium soap, gum rosin disproportionated rosin, potassium salt or sodium salt thereof. Gum rosin is mainly composed of abithienic acid, and preferably contains 60% by mass or more of abithienic acid.
Surfactants derived from N-acylamino acids include N-lauroyl sarcosine, N-cocoyl sarcosine, N-myristyl sarcosine, N-partoyl sarcosine, N-oleoyl sarcosine, their potassium salts Or a sodium salt etc. are mentioned.

The amount of the surfactant derived from gum rosin or the surfactant derived from N-acylamino acid is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the graft copolymer (A). 0.05 to 5 parts by mass is more preferable, and 0.1 to 4 parts by mass is particularly preferable. If the usage-amount of surfactant is less than 0.01 mass part, there exists a possibility that stability of polyacetal resin (B) cannot be hold | maintained. When the usage-amount of surfactant exceeds 10 mass parts, there exists a possibility that the mechanical physical property of a molded article may fall.
In the present invention, in order to perform stable polymerization, other surfactants such as sulfonic acid surfactants, sulfosuccinic acid surfactants, sulfuric acid, and the like may be used within the range not inhibiting the intended purpose of the present invention. Surfactants, fatty acid surfactants, succinic acid surfactants, and the like may be used in combination.

  As a rubbery polymer (R) obtained by polymerizing monomers constituting a rubbery polymer in the presence of a surfactant derived from gum rosin or a surfactant derived from N-acylamino acid, , Diene rubbers, acrylic rubbers, silicone rubbers, and composite rubbers obtained by combining these.

(Diene rubber)
The diene rubber is preferably a 1,3-butadiene homopolymer or copolymer (hereinafter referred to as a butadiene rubber polymer). The butadiene rubber polymer is obtained by polymerizing 1,3-butadiene, if necessary, a crosslinkable monomer and a vinyl monomer copolymerizable with 1,3-butadiene.

  Examples of the crosslinkable monomer include aromatic polyfunctional vinyl compounds such as divinylbenzene and divinyltoluene; dicarboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate and 1,3-butanediol diacrylate; trimethacrylic acid Examples include esters; triacrylic acid esters; carboxylic acid allyl esters such as allyl acrylate and allyl methacrylate; and di- or triallyl compounds such as diallyl phthalate, diallyl sebacate, and triallyl triazine. A crosslinkable monomer may be used individually by 1 type, and may use 2 or more types together.

  Examples of vinyl monomers that can be copolymerized with 1,3-butadiene (excluding crosslinkable monomers; hereinafter the same) include aromatic vinyl such as styrene and α-methylstyrene; methyl methacrylate, ethyl Alkyl methacrylates such as methacrylate; alkyl acrylates such as ethyl acrylate and n-butyl acrylate; unsaturated nitriles such as acrylonitrile and methacrylonitrile; vinyl ethers such as methyl vinyl ether and butyl vinyl ether; vinyl halides such as vinyl chloride and vinyl bromide; Examples thereof include vinylidene halides such as vinylidene chloride and vinylidene bromide; glycidyl group-containing vinyl monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and ethylene glycol glycidyl ether. A vinyl monomer may be used individually by 1 type, and may use 2 or more types together.

  The proportion of each monomer is 65 to 100 parts by mass of 1,3-butadiene and 0 to 10 for the crosslinkable monomer when the total amount of monomers used for the polymerization of the butadiene rubber polymer is 100 parts by mass. It is preferable to use a vinyl monomer that can be copolymerized with 1,3-butadiene, with the remainder being part by mass. By making 1,3-butadiene 65 mass parts or more, a good impact resistance imparting effect can be obtained.

  The diene rubber preferably has a mass average particle diameter (dw) of 80 to 800 nm, more preferably is enlarged by an acid or salt, and is particularly preferably enlarged by an organic acid copolymer. .

  As an organic acid copolymer, a mixture containing alkyl acrylate and at least one unsaturated acid monomer copolymerizable with alkyl acrylate is polymerized in the presence of an anionic surfactant as an emulsifier. Latex having a pH of 4 or higher is preferred. Moreover, 70-99 mass% of alkyl acrylate is preferable in 100 mass% of all monomers, and 1-30 mass% of an unsaturated acid monomer is preferable. When the unsaturated acid monomer is less than 1% by mass, the effect of improving the impact strength may not appear.

Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and lauryl acrylate.
Examples of the unsaturated acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, cinnamic acid, maleic anhydride, and butenetricarboxylic acid.
You may copolymerize another monomer as needed. Examples of other monomers include styrene, methyl methacrylate, acrylonitrile, and butadiene.

  A polymer can be obtained by using any of anionic, cationic, and nonionic emulsifiers as emulsifiers, but the enlargement ability varies significantly depending on the type of emulsifier. From such a viewpoint, an anionic surfactant which is an anionic emulsifier is preferable. From the same viewpoint, anionic surfactants other than phosphate ester salts and alkylsulfosuccinates are preferred.

  When a small amount of the organic acid copolymer latex is added to the diene rubber latex under appropriate conditions, sufficient enlargement of the diene rubber can be achieved. If appropriate conditions are selected, by adding 0.01 part by weight (solid content) of the organic acid copolymer to 100 parts by weight (solid content) of the diene rubber, the diene rubber latex contains In some cases, the particle diameter of the diene rubber may be enlarged to more than twice, and by adding 0.5 part by mass of an organic acid copolymer, the diene rubber having a particle diameter of 70 nm is enlarged to 300 nm or more. You can also.

  The addition amount of the organic acid copolymer is preferably 0.01 parts by mass (solid content) or more in order to realize sufficient enlargement with respect to 100 parts by mass (solid content) of the diene rubber. Is preferably 10 parts by mass (solid content) or less in order to avoid damage.

(Composite rubber)
Examples of the composite rubber include a composite rubber containing a polyorganosiloxane and a polyalkyl (meth) acrylate rubber, a composite acrylic rubber having two or more different glass transition temperatures, and the like.

<Graft copolymer (A)>
The graft copolymer (A) is a graft polymer obtained by graft polymerization of a vinyl monomer to the rubber polymer (R). The graft copolymer (A) is added to the polyacetal resin (B) as an impact strength modifier.

(Vinyl monomer)
Examples of vinyl monomers include aromatic vinyl such as styrene, α-methylstyrene, and vinyl toluene; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and 2-ethylhexyl methacrylate; methyl acrylate, ethyl acrylate, butyl acrylate, and the like. An unsaturated nitrile such as acrylonitrile or methacrylonitrile. A vinyl monomer may be used individually by 1 type, and may use 2 or more types together.

  The ratio of the rubber part derived from the rubbery polymer (R) and the hard graft part derived from the vinyl monomer in the graft copolymer (A) is 100 masses of the graft copolymer (A). %, The rubber part is preferably 40 to 99% by mass, the graft part is preferably 60 to 1% by mass, the rubber part is 50 to 95% by mass, the graft part is preferably 50 to 5% by mass, the rubber part is 60 to 92% by mass, The graft part is particularly preferably 40 to 8% by mass.

  Various polymerization methods can be used for producing the graft copolymer (A), and an emulsion polymerization method is preferred. Specifically, a method in which a vinyl monomer is polymerized into a latex of the rubber-like polymer (R) by batch addition, split addition, or continuous addition to polymerize the vinyl monomer.

  The graft copolymer (A) in the latex obtained by the emulsion polymerization method is coagulated, and the graft copolymer (A) is recovered from the latex as a powder. It is preferable from the point. Examples of the coagulant for coagulating the graft copolymer (A) in the latex include acids and salts, and calcium-based salts are preferred.

<Polyacetal resin (B)>
The polyacetal resin (B) is preferably a polyoxymethylene copolymer having an oxymethylene group as a main repeating unit and an oxyalkylene group unit having 2 or more carbon atoms.

The polyacetal resin (B) preferably has a content of oxyalkylene group units having 2 or more carbon atoms of 0.5 to 3.0% by mass, more preferably 0.6 to 2.0% by mass, The thing of 0.7-1.6 mass% is especially preferable. If the content of oxyalkylene group units having 2 or more carbon atoms is too small, the stability of the polyacetal resin (B) to heat and chemicals will be insufficient, and the long-term durability of various properties such as strength and accuracy of the molded product will be reduced. There is a risk. When the content of the oxyalkylene group unit having 2 or more carbon atoms is too large, the strength and rigidity of the molded product tend to decrease.
A polyacetal resin (B) may be used individually by 1 type, and may use 2 or more types together.

  The polyacetal resin (B) has, as a main monomer, formaldehyde or trioxane which is a cyclic oligomer thereof, ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3,5-trioxepane, 1,4-butanediol formal, diethylene glycol formal, etc. These are obtained by copolymerizing at least one selected from the group consisting of cyclic ethers having at least one carbon-carbon bond and cyclic acetals in the presence of a cationic catalyst. As the comonomer, 1,3-dioxolane and / or 1,3,5-trioxepane that does not cause chain transfer in the polymer is preferable because of its good dispersibility.

The polyacetal resin (B) can be produced by the same apparatus and method as the known trioxane copolymerization method.
In the production of the polyacetal resin (B), any of batch-type and continuous-type production methods may be employed, and any polymerization method such as melt polymerization or solution bulk polymerization may be employed. In consideration of industrial productivity, a continuous bulk polymerization method using a liquid monomer as a raw material and obtaining a solid powdery bulk polymer as the polymerization proceeds in the presence of an inert liquid catalyst as necessary is preferable.

  During the polymerization, a chain transfer agent may be added to adjust the molecular weight of the polyacetal resin (B). Examples of the chain transfer agent include methylal, ethylal, and butyral. These may be used alone or in combination of two or more. The addition amount of the chain transfer agent is appropriately adjusted within the range of 0 to 1000 ppm depending on the molecular weight of the polyacetal resin (B).

  Examples of the polymerization catalyst include known cationically active catalysts. Cationic active catalysts include Lewis acids (borides such as boron, tin, titanium, phosphorus, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, Arsenic fluoride, antimony pentafluoride, complex compounds or salts thereof), protonic acid (eg, trifluoromethanesulfonic acid, perchloric acid), ester of protonic acid (ester of perchloric acid and lower aliphatic alcohol, eg, perchlor Acid tertiary butyl ester), protonic acid anhydrides (mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids, eg acetyl perchlorite), isopolyacids, heteropolyacids (eg phosphomolybdic acid), triethyl Oxonium hexafluorophosphate, triphenylmethyl hexafluoroarzena DOO, acetyl hexafluoro borate and the like. Among these, boron trifluoride or a coordination compound of boron trifluoride and an organic compound (for example, ethers) is preferable. These polymerization catalysts may be used individually by 1 type, and may use 2 or more types together. The addition amount of the polymerization catalyst is usually 10 to 300 ppm with respect to the total amount of the main monomer and the comonomer.

Examples of the polymerization apparatus include a continuous polymerization apparatus for trioxane such as a kneader, a twin screw continuous extrusion mixer, and a twin screw paddle type continuous mixer. The apparatus may be divided into two or more stages as long as it is a closed system. The thing provided with the grinding | pulverization function in which the solid polymer produced | generated by a polymerization reaction is obtained with a fine form is preferable.
The polymerization temperature is usually 64 to 120 ° C., and a relatively low temperature is suitable within this range. The preferred range of the polymerization time varies depending on the amount of the catalyst, and is usually 0.5 to 100 minutes.

  It is preferable to deactivate the polymerization catalyst by immediately mixing a deactivator with the crude polymer discharged from the polymerization apparatus. Examples of the deactivator include a solution in which an amine such as triethylamine or triethanolamine is mixed with an inorganic alkaline substance such as sodium fluoride or potassium fluoride. The quenching agent is preferably an aqueous solution.

  The polyacetal resin (B), after deactivating the polymerization catalyst, is subjected to washing, separation and recovery of unreacted monomers, drying, etc., if necessary, and terminal stabilization such as decomposition and removal of unstable terminal parts as necessary. And, if necessary, additives such as various stabilizers and processability improvers are added, and then melt-kneaded pellets are produced.

Examples of the additive include an antioxidant, a nitrogen-containing compound, a heat resistance stabilizer, an ultraviolet absorber, a light stabilizer, a lubricant, and a plasticizer.
Antioxidants include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl). ) Propionate], pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol bis [3- (3-t-butyl-5-methyl-4-hydroxy) Phenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, n-octadecyl-3- (4′-hydroxy-) 3 ', 5'-di-t-butylphenyl) propionate, 4,4'-methylenebis (2,6-di-t-butylphenol), 4,4'-butylidenebi -(6-t-butyl-3-methylphenol), 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethyl Ethyl} 2,4,8,10-tetraoxaspiro [5,5] undecane, di-stearyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate, 2-t-butyl-6- (3 -T-butyl-5-methyl-2-hydroxybenzyl) -4-methylphenyl acrylate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), etc. Hindered phenols and the like.

Examples of the nitrogen-containing compound include polyamides such as nylon 6 · 10, nylon 6 · 66 · 610, and polyacrylamide; polycondensates of melamine, dicyandiamide, and the like with formaldehyde.
Examples of the heat stabilizer include metal-containing compounds such as sodium salts, potassium salts, magnesium salts, calcium salts, and barium salts of higher fatty acids such as stearic acid or substituted higher fatty acids having a substituent such as a hydroxyl group.
Examples of the ultraviolet absorber include benzotriazoles such as 2- [2-hydroxy-3,5-bis- (α, α′-dimethylbenzyl) phenyl] benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone. Etc.
Examples of the light stabilizer include hindered amines such as 4-acetoxy-2,2,6,6-tetramethylpiperidine and bis (2,2,6,6-tetramethyl-4-piperidyl) adipate.
Examples of the lubricant include higher fatty acid esters such as glycerin monostearate and pentaerythritol tristearate; higher fatty acid amides such as ethylenebis (stearylamide).
Examples of the plasticizer include polyethylene glycol and polyoxyethylene polypropylene copolymer.

Antioxidants include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol bis [3- (3,5-di-tert-butyl-4). -Hydroxyphenyl) propionate], 3,9-bis- {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy-] 1,1-dimethylethyl} -2,4 Hindered phenols such as 8,10-tetraoxaspiro [5,5] undecane are preferred.
As the nitrogen-containing compound, polycondensation of melamine, dicyandiamide or the like with formaldehyde is preferable.
As the metal-containing compound, magnesium salts and calcium salts of higher fatty acids or substituted higher fatty acids are preferable.

<Thermoplastic resin composition>
The thermoplastic resin composition of the present invention contains a graft copolymer (A) and a polyacetal resin (B).
The blending ratio of the graft copolymer (A) to the polyacetal resin (B) is preferably 1 to 50% by mass of the graft copolymer (A) and 99 to 50% by mass of the polyacetal resin (B). A) 5 to 40% by mass, polyacetal resin (B) 95 to 60% by mass is more preferable, graft copolymer (A) 7 to 35% by mass, and polyacetal resin (B) 93 to 65% by mass are particularly preferable (however, The total of the graft copolymer (A) and the polyacetal resin (B) is 100% by mass). When the graft copolymer (A) is less than 1% by mass, a molded article having desired impact resistance may not be obtained. When the graft copolymer (A) exceeds 50% by mass, the mechanical properties of the obtained molded product may be impaired.

  The thermoplastic resin composition of the present invention may be prepared by any method that can blend a predetermined amount of the graft copolymer (A) with respect to the polyacetal resin (B). For example, the polyacetal resin (B) and the graft copolymer (A) are mixed directly or in advance, and then kneaded with a single or twin screw extruder or the like, and pelletized to prepare a thermoplastic resin composition. be able to. In preparing the thermoplastic resin composition, it is preferable to pulverize part or all of the polyacetal resin (B) in advance in order to improve the dispersibility of other components to be blended therein.

In the thermoplastic resin composition of the present invention, the following thermoplastic resins may be blended as long as the original physical properties are not impaired.
Thermoplastic resins include vinyl chloride resin (PVC), chlorinated polyethylene resin, chlorinated vinyl chloride resin, vinylidene chloride resin and other hard, semi-rigid and soft chlorine-containing resins; polypropylene (PP), polyethylene (PE) Olefin resins such as: polystyrene (PS), high impact polystyrene (HIPS), (meth) acrylate-styrene copolymer (MS), styrene-acrylonitrile copolymer (SAN), styrene-maleic anhydride copolymer ( Styrenic resins (St resin) such as SMA), acrylonitrile-butadiene-styrene resin (ABS), acrylate-styrene-acrylonitrile resin (ASA), acrylonitrile-ethylenepropylene rubber-styrene resin (AES); polymethyl methacrylate (PMMA) ) Etc. Ryl resin (Ac resin); Polycarbonate resin (PC resin); Polyamide resin (PA resin); Polyester resin (PEs resin) such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); Polylactic acid resin, thermoplastic polyvinyl alcohol resin, polybutylene succinate, other biodegradable natural raw materials, environmentally friendly resins derived from petroleum raw materials (biodegradable resins); (modified) polyphenylene ether resins (PPE resins) , Polyoxymethylene resin (POM resin), polysulfone resin (PSO resin), polyarylate resin (PAr resin), polyphenylene resin (PPS resin), thermoplastic polyurethane resin (PU resin) ) Engineering plastics; styrene-based elastomer -Thermoplastic elastomers (TPE) such as olefin elastomers, vinyl chloride elastomers, urethane elastomers, polyester elastomers, polyamide elastomers, fluorine elastomers, 1,2-polybutadiene, trans 1,4-polyisoprene; PC / PC resin such as ABS / St resin resin alloy, PVC resin such as PVC / ABS / St resin resin alloy, PA resin such as PA / ABS / St resin resin alloy, PA resin / TPE alloy, PA / Alloys between PA resins such as PP / polyolefin resins, PBT resins / TPE, PC resins such as PC / PBT / PEs resins, polyolefin resins / TPE, olefin resins such as PP / PE, P such as PPE / HIPS, PPE / PBT, PPE / PA Examples thereof include polymer alloys such as PE resin alloys, PVC resins such as PVC / PMMA / Ac resin alloys, and the like.

<Molded product>
The molded article of the present invention is formed by molding a thermoplastic resin composition.
As a forming method, a method of forming pellets prepared to have a desired composition; after preparing a plurality of types of pellets having different compositions, these are mixed (diluted) at a predetermined ratio and used for forming; A method of obtaining a desired composition can be employed.
Examples of the molded article of the present invention include resin gears and mechanical parts in OA equipment, information equipment, home appliances, automobiles, clothing, stationery, sundries, building materials, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “parts” and “%” in the examples represent “parts by mass” and “mass%”, respectively.

The mass average particle size and particle size distribution of the polymer in the latex in the production example were measured as follows.
Using the obtained latex diluted with distilled water as a sample, a mass average particle size and a particle size distribution were measured using a CHDF2000 type particle size distribution meter manufactured by MATEC USA. The measurement conditions were standard conditions recommended by MATEC. Specifically, using a dedicated capillary cartridge for particle separation and a carrier liquid, the liquidity is neutral, the flow rate is 1.4 mL / min, the pressure is 28 MPa, and the temperature is 35 ° C., and the concentration is 3%. This was measured using 0.1 mL of diluted latex sample. As the standard particle size substance, a total of 12 monodisperse polystyrenes having a known particle size manufactured by DUKE Co., Ltd. in the United States were used in the range of 0.03 μm to 0.8 μm.

[Production Example 1]
Production of rubber polymer (R-1) latex:
1,3-butadiene 100 parts, t-dodecyl mercaptan 0.4 part, gum rosin-based disproportionated rosin potassium soap (manufactured by Toho Chemical Co., Ltd., Diplodine K-25) 1.0 part, bovine fatty acid potassium soap (manufactured by Kao, KS Soap) 0.5 parts, 0.24 parts diisopropylbenzene peroxide, and 170 parts deionized water were charged into a 70 L autoclave and when the temperature reached 43 ° C., 0.003 part ferrous sulfate, dextst A redox initiator consisting of 0.3 part of rose, 0.3 part of sodium pyrophosphate, and 5 parts of deionized water was added to the autoclave, and after the polymerization was started, the temperature was further raised to 60 ° C. Reaction was performed for 8 hours from the start of polymerization to obtain a rubbery polymer (R-1) latex. The mass average particle diameter of the rubber-like polymer (R-1) in the obtained latex was 92 nm.

[Production Example 2]
Production of rubber polymer (R-2) latex:
Surfactant, gum rosin-based disproportionated rosin potassium soap 1.0 part, bovine fatty acid potassium soap 0.5 part, N-lauroyl sarcosinate sodium (manufactured by Nikko Chemicals, Sarcosinate LN) 1.0 part, bovine fatty acid A rubber polymer (R-2) latex was obtained in the same manner as in Production Example 1 except that 0.5 part of sodium soap (manufactured by Kao, NS soap) was used. The mass average particle diameter of the rubber polymer (R-2) in the obtained latex was 90 nm.

[Production Example 3]
Production of rubber polymer (R-3) latex:
Surfactant, 1.0 part of gum rosin-based disproportionated rosin potassium soap and 0.5 part of bovine fatty acid potassium soap, 0.75 part of gum rosin-based disproportionated rosin sodium soap (Diplodin N-20 manufactured by Toho Chemical) A rubbery polymer (R-3) latex was obtained in the same manner as in Production Example 1, except that 0.75 part of sodium N-lauroyl sarcosinate was used. The mass average particle diameter of the rubber-like polymer (R-3) in the obtained latex was 95 nm.

[Production Example 4]
Production of rubber polymer (R′-4) latex:
A surfactant, 1.0 part of gum rosin-based disproportionated rosin potassium soap, 0.5 part of bovine fatty acid potassium soap, and the same procedure as in Production Example 1 except that only 1.7 parts of bovine fatty acid potassium soap were used. A rubbery polymer (R′-4) latex was obtained. The mass average particle diameter of the rubber-like polymer (R′-4) in the obtained latex was 90 nm.

[Production Example 5]
Production of organic acid copolymer emulsion:
A reactor was charged with 85 parts of n-butyl acrylate, 15 parts of methacrylic acid, 2.0 parts of sodium oleate, 1.0 part of sodium dioctylsulfosuccinate, 0.5 part of cumene hydroperoxide, and 200 parts of deionized water. A redox initiator consisting of 0.003 part of ferrous sulfate, 0.009 part of ethylenediaminetetraacetic acid disodium salt, 0.26 part of Rongalite, and 5 parts of deionized water is added to the reactor and 4 Polymerization was performed for a time to obtain an organic acid copolymer emulsion having a conversion rate of 98% and a pH of 5.0.

[Production Example 6]
Production of graft copolymer (A-1):
To 75 parts (solid content) of the rubber-like polymer (R-1) latex in the reactor, 2.0 parts (solid content) of an organic acid copolymer emulsion was added and stirred at room temperature for 30 minutes.

  Thereafter, 0.5 part of sodium oleate and 0.6 part of sodium formaldehyde sulfoxylate were added to the reactor, the internal temperature was maintained at 70 ° C., and 9.0 parts of methyl methacrylate and n-butyl acrylate 1 0.0 part, and a mixture of cumene hydroxy peroxide (0.2 parts with respect to a total of 100 parts of methyl methacrylate and n-butyl acrylate) was added dropwise over 1 hour, and then kept for 1 hour. A graft polymerization step was performed.

  Thereafter, in the presence of the polymer obtained in the first graft polymerization step, 12.5 parts of styrene as the second stage, and cumene hydroxy peroxide (an amount of 0.2 parts with respect to 100 parts of styrene). The mixture was added dropwise over 1 hour and then held for 3 hours to perform the second graft polymerization step.

  Then, in the presence of the polymer obtained in the second graft polymerization step, as the third stage, 2.5 parts of methyl methacrylate and an amount of 0.1 part of cumene hydroxyperoxide (100 parts of methyl methacrylate) ) Was added dropwise over 0.5 hour, held for 1 hour, and the third graft polymerization step was completed to obtain a graft copolymer (A-1) latex. The particle size distribution of the graft copolymer (A-1) in the latex was measured. The results are shown in Table 1.

  To the obtained graft copolymer (A-1) latex, 0.5 part of triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] and dilaurylthiodipro After adding 0.5 parts of pionate, 60 parts of 0.5% aqueous calcium acetate solution was added to coagulate the graft copolymer (A-1), and heat-treated at 90 ° C. to solidify. Thereafter, the coagulated product was washed with warm water and further dried to obtain a graft copolymer (A-1).

[Production Example 7]
Production of graft copolymer (A-2):
A graft copolymer (A-2) was obtained in the same manner as in Production Example 6 except that the rubber polymer (R-1) latex was changed to a rubber polymer (R-2) latex.

[Production Example 8]
Production of graft copolymer (A-3):
A graft copolymer (A-3) was obtained in the same manner as in Production Example 6 except that the rubber polymer (R-1) latex was changed to a rubber polymer (R-3) latex.

[Production Example 9]
Production of graft copolymer (A-4):
In Production Example 8, rubber graft graft copolymer was prepared in the same manner as in Production Example 8, except that the organic acid copolymer emulsion was not enlarged and the rubber polymer (R-3) latex was directly grafted. A polymer (A-4) was obtained.

[Production Example 10]
Production of graft copolymer (A′-5):
The rubber polymer (R'-4) latex is used as the rubber polymer (R'-4) latex, and the rubber polymer (R'-4) latex is not enlarged using an organic acid copolymer emulsion. A graft copolymer (A′-5) was obtained in the same manner as in Production Example 6 except that the graft polymerization was performed directly on the mixture, and calcium acetate as a coagulant in the coagulation step was changed to sulfuric acid.

[Production Example 11]
Production of polyacetal resin (B-1):
A mixture of trioxane and a small amount of 1,3-dioxolane (comonomer) is polymerized in the presence of boron trifluoride etherate (catalyst) to obtain a polyacetal resin (B-1) containing 1.50% oxyethylene groups. After being obtained, the catalyst was deactivated with triethylamine (deactivator), and further pelletized through a terminal stabilization step.

[Examples 1 to 4, Comparative Example 1]
In the proportion shown in Table 1, the polyacetal resin (B-1) is blended with the graft copolymers (A-1) to (A-4) and (A′-5) as impact strength modifiers, and the plastic laboratory. It was pelletized with a BT30 type twin screw extruder manufactured by Research Laboratory, and a thermoplastic resin composition was obtained.
Subsequently, in order to perform various evaluation tests, the obtained thermoplastic resin composition was injection-molded under normal conditions with a SAV60 type injection molding machine manufactured by Sanjo Kikai, and a test piece was produced.

The following evaluation tests were performed on the thermoplastic resin composition and the test piece.
(1) Evaluation of degradation resistance of polyacetal resin:
The thermoplastic resin composition pellets were weighed and charged for 5 minutes to a 2.1 mm diameter die mounted on a Techno Seven melt indexer heated to 210 ° C., and then loaded for 10 minutes. The mass (MI) flowing out in 30 seconds was measured for the amount of strands extruded thereby. Similarly, MI was measured after holding for 30 minutes. The ΔMI obtained by subtracting the MI when held for 5 minutes from the MI when held for 30 minutes was used as a criterion for determination of decomposition resistance. A positive value or a negative value as small as possible was judged as good.
At the same time, the coloring and odor of the strands when held for 30 minutes were evaluated. As for coloring, the case with almost no change was evaluated as ◯, and the color change was evaluated as ×. As for odors, those that hardly scented were evaluated as ○, and those that scented were evaluated as ×.

(2) Izod impact strength:
The Izod impact strength of the specimen was measured at 23 ° C. according to ASTM D256. A 1/8 inch thick, notched specimen was used.

(3) Flexural modulus:
The flexural modulus of the specimen was measured at 23 ° C. according to ASTM D790. The thickness of the test piece was 1/4 inch.

  As shown in Table 1, in the examples, the polyacetal resin has good decomposition resistance (stability) and excellent mechanical properties of the molded product. In particular, those using a graft copolymer enlarged with an organic acid copolymer exhibit excellent physical properties in terms of impact resistance. On the other hand, the comparative example was inferior to the decomposition resistance of the polyacetal resin. This shows the effect of the present invention.

The thermoplastic resin composition of the present invention is excellent in stability and has excellent mechanical properties of a molded product to be obtained. Therefore, it is used for OA equipment, information equipment, home appliances, automobiles, clothing, stationery, miscellaneous goods, building materials, etc. It is suitably used for resin gears, mechanical parts, and the like.

Claims (2)

A graft copolymer (A) obtained by graft-polymerizing a vinyl monomer to the rubber polymer (R);
Containing a polyacetal resin (B),
The rubbery polymer (R) is obtained by polymerizing monomers constituting the rubbery polymer in the presence of a surfactant derived from gum rosin or a surfactant derived from N-acylamino acid. The thermoplastic resin composition characterized by the above-mentioned. A molded article formed by molding the thermoplastic resin composition according to claim 1.