JP2005248073A - Thermoplastic resin composition and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a thermoplastic resin composition which is prevented from decomposition of a polyacetal resin and has high impact resistance, and to provide a manufacturing method therefor. <P>SOLUTION: The thermoplastic resin composition comprises the polyacetal resin, and an impact strength modifier comprising a reactive surfactant and a grafted polymer having at least a part of the surfactant chemically bonded thereto. The manufacturing method for the thermoplastic resin composition comprises a manufacturing step of the impact strength modifier comprising emulsion-polymerizing a monomer onto a rubber component in the presence of the reactive surfactant and subsequently removing water to obtain the impact strength modifier, and a compounding step for compounding the impact strength modifier with the polyacetal resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoplastic resin composition that contains a polyacetal resin and can be used as a material for resin gears, mechanical parts, and the like, and a method for producing the same.

  Polyacetal resin is an engineering plastic with excellent mechanical strength, fatigue resistance, slidability, chemical resistance, etc., used for OA equipment, information equipment, home appliances, automobiles, clothing, stationery, sundries, building materials, etc. It is widely used as a material for resin gears and mechanism parts. In particular, in addition to the above characteristics, mass production is possible at a low cost, and therefore, it is widely used as a material for buttons, clips, and gears that require the above characteristics.

When used as a material for buttons, clips, etc., performance such as high impact resistance, low wear resistance, and high accuracy is required. In particular, it is important to have excellent impact resistance.
Here, as a means for improving impact resistance, it is conceivable to add reinforcing fillers such as inorganic fillers such as glass fiber, carbon fiber, potassium titanate whisker, calcium carbonate, and talc to the polyacetal resin. . However, the reinforcing filler is generally harder than the polyacetal resin, and the reinforcing filler scrapes the polyacetal resin during sliding, which may increase the amount of wear.
Therefore, as a means for improving impact resistance without impairing the features of polyacetal resin such as slidability and dimensional stability, Patent Document 1 discloses an acrylic cross-linked rubber graft copolymer as an impact strength modifier in a specific range. It has been proposed to add. Specifically, it is proposed to add a core-shell type graft copolymer, and in that case, it is shown that the impact resistance is higher than that in the case of adding a urethane elastomer.

However, when the core-shell type graft copolymer described in Patent Document 1 obtained by general emulsion polymerization is added to the polyacetal resin, the polyacetal resin may be decomposed. This is because the polyacetal resin is easily broken due to the polymer structure and is relatively easily decomposed by acid, alkali, and other factors. The surfactant, catalyst, alkali metal contained in the graft copolymer. Etc., the polyacetal resin was decomposed. As a result, the original mechanical properties of the polyacetal resin could not be fully exhibited.
For this reason, a method for improving the resistance to degradation of the polyacetal resin itself or a method for adding a pH adjuster has been proposed and implemented. Patent Document 2 discloses a polymer in which anion is not substantially detected, and Patent Document 3 discloses a resin to which a specific stabilizer is added for the purpose of improving heat aging caused by thermal decomposition or the like. A composition is disclosed.
JP-A-2-129266 JP-A-6-1000075 JP 7-316393 A

However, the methods proposed so far have not been able to enhance the impact resistance while sufficiently preventing the decomposition of polyacetal.
An object of the present invention is to provide a thermoplastic resin composition that prevents decomposition of a polyacetal resin and has high impact resistance, and a method for producing the same.

The thermoplastic resin composition of the present invention comprises a polyacetal resin,
It contains a surfactant having reactivity and an impact strength modifier containing a graft polymer in which at least a part of the surfactant is chemically bonded.
The method for producing the thermoplastic resin composition of the present invention is an impact which obtains an impact strength modifier by removing water after emulsion polymerization of a monomer with a rubber component in the presence of a reactive surfactant. Strength modifier manufacturing process,
It has the compounding process which mix | blends this impact strength modifier and polyacetal resin, It is characterized by the above-mentioned.

  In the present invention, since the impact resistance is high and the polyacetal resin is prevented from being decomposed, the excellent mechanical properties inherent in the polyacetal resin are not impaired.

Hereinafter, the present invention will be described in detail.
The thermoplastic resin composition of the present invention contains a polyacetal resin and a specific impact strength modifier.

"Polyacetal resin"
The polyacetal resin is not particularly limited, but a resin mainly composed of a polyoxymethylene copolymer having an oxymethylene group as a main repeating unit and an oxyalkylene group having 2 or more carbon atoms is preferable.
Specifically, formaldehyde or trioxane, which is a cyclic oligomer thereof, is used as a main monomer, and ethylene oxide, propylene oxide, 1,3-dioxolane, 1,3,5-trioxepane, 1,4-butanediol formal, diethylene glycol formal, etc. What is obtained by copolymerizing in the presence of a cationic catalyst using at least one selected from cyclic ethers and / or cyclic acetals having at least one carbon-carbon bond as a comonomer is preferable. As the comonomer, 1,3-dioxolane and / or 1,3,5-trioxepane, which do not cause chain transfer in the polymer, is preferable because of good comonomer dispersibility.

  As a polyoxymethylene copolymer, a copolymer containing an oxyalkylene group having 2 or more carbon atoms is suitable as a comonomer, but the content of oxyalkylene group units is 0.5 to 3.0% by mass. It is preferable that it is 0.6 to 2.0% by mass, and 0.7 to 1.6% by mass is particularly preferable. If the comonomer content is too low, the stability of the copolymer to heat and chemicals may be insufficient, and the long-term durability of various properties such as strength and accuracy may be reduced. If the comonomer content is too high, strength and rigidity may be reduced. Tends to decrease, which is not preferable.

The polyoxymethylene copolymer can be produced by the same equipment and method as the conventionally known trioxane copolymerization method.
In the production of the polyoxymethylene copolymer, batch production, continuous production, any production method may be employed, and any polymerization method such as melt polymerization, solution bulk polymerization, etc. 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.

  At the time of polymerization, a chain transfer agent can be added to adjust the molecular weight of the polyoxymethylene copolymer. Examples of the chain transfer agent include methylal, ethylal, butyral and the like. Although the addition amount of a chain transfer agent is not specifically limited, It is suitably adjusted within the range of 0-1000 ppm according to the molecular weight of a copolymer.

  As the polymerization catalyst, a known cationically active catalyst can be used. Cationic active catalysts include Lewis acids, especially halides such as boron, tin, titanium, phosphorus, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, Arsenic pentafluoride and antimony pentafluoride and compounds such as complex compounds or salts thereof, protic acids such as trifluoromethanesulfonic acid, perchloric acid, esters of protic acids, especially esters of perchloric acid and lower aliphatic alcohols (for example (Tertiary butyl ester of perchloric acid), anhydrides of protonic acids, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids (especially acetyl perchlorite), or isopolyacids, heteropolyacids (eg phosphomolybdic acid) Or triethyloxonium hexafluorophosphate, triphenylmethyl Sa fluoro Aruze diisocyanate, acetyl hexafluoro borate and the like. Among these, boron trifluoride and a coordination compound of boron trifluoride and an organic compound (for example, ethers) are preferable. The addition amount of these catalysts is generally 10 to 300 ppm with respect to the total amount of the main monomer and comonomer.

Although it does not specifically limit as a superposition | polymerization apparatus, Continuous superposition | polymerization apparatuses, such as a kneader, a twin screw type continuous extrusion mixer, a twin screw paddle type continuous mixer, can be used. If the apparatus to be used is a closed system, it may be divided into two or more stages. However, 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 not particularly limited, but is generally from 64 to 120 ° C. A relatively low temperature is preferable within this range.
The preferred range of the polymerization time varies depending on the amount of the catalyst and is not particularly limited, but is generally 0.5 to 100 minutes.
After a suitable polymerization time has elapsed, it is preferable to deactivate the polymerization catalyst by immediately bringing the deactivator into mixed contact with the crude polymer discharged from the polymerization apparatus. Examples of the quencher include a solution obtained by mixing an amine such as triethylamine or triethanolamine with an inorganic alkaline substance such as sodium fluoride or potassium fluoride. The deactivator used is preferably an aqueous solution.

After the polyacetal resin has deactivated the polymerization catalyst, it undergoes washing, separation / recovery of unreacted monomers, drying, etc., if necessary, and terminal stabilization steps such as decomposition and removal of unstable terminal parts as necessary. Then, if necessary, additives such as various stabilizers and processability improvers are added, and then melt-kneaded pellets are produced.
Examples of organic compounds suitable as a stabilizer and a processability improver include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 1,6-hexanediol-bis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol bis [3- ( 3-tert-butyl-5-methyl-4-hydroxyphenyl) 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- -T-butylphenol), 4,4'-butylidenebis- (6-t-butyl-3-methylphenol), 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5- Methylphenyl) propionyloxy] -1,1-dimethylethyl} 2,4,8,10-tetraoxaspiro [5,5] undecane, di-stearyl-3,5-di-t-butyl-4-hydroxybenzyl Phosphonate, 2-t-butyl-6- (3-t-butyl-5-methyl-2-hydroxybenzyl) -4-methylphenyl acrylate, N, N′-hexamethylenebis (3,5-di-t- Antioxidants typified by hindered phenols such as butyl-4-hydroxy-hydrocinnamamide), nylon 6,10, nylon 6,66,610, polyacrylamide, etc. Of higher fatty acids such as amide, melamine, dicyandiamide, etc. and polycondensates with formaldehyde, higher fatty acids such as stearic acid such as sodium, potassium, magnesium, calcium and barium, and substituted higher fatty acids having substituents such as hydroxyl groups. Heat-resistant stabilizers typified by metal-containing compounds such as salts, benzotriazoles such as 2- [2-hydroxy-3,5-bis- (α, α′-dimethylbenzyl) phenyl] benzotriazole, 2-hydroxy UV absorbers represented by benzophenones such as -4-methoxybenzophenone, 4-acetoxy-2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4- Piperidyl) Light stabilizers typified by hindered amines such as adipate, glycerin monostea Examples thereof include higher fatty acid esters such as rate and pentaerythritol tristearate, lubricants represented by higher fatty acid amides such as ethylene bis (stearylamide), and plasticizers such as polyethylene glycol and polyoxyethylene polypropylene copolymers. These may be used alone or in combination of two or more.
Among them, as the antioxidant, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol bis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate], 3,9-bis- {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) furopionyloxy-] 1,1-dimethylethyl } Hindered phenols such as -2,4,8,10-tetraoxaspiro [5,5] undecane are preferred, and the nitrogen-containing compound is preferably polycondensation with melamine, dicyandiamide or the like and formaldehyde, and a metal-containing compound As salts thereof, magnesium and calcium higher fatty acids and salts of substituted higher fatty acids are preferred.
The total amount of the compound added as a stabilizer to the polyacetal resin is not particularly limited, but is preferably 0.1 to 2.0% by mass, and particularly preferably 0.1 to 1.0% by mass.

"Impact strength modifier"
The impact strength modifier includes a reactive surfactant (hereinafter abbreviated as a reactive surfactant) and a graft polymer in which at least a part of the reactive surfactant is chemically bonded. . Thus, since at least a part of the reactive surfactant is chemically bonded to the graft polymer, bleeding or the like does not occur in the molten state, and as a result, the decomposition of the polyacetal resin can be suppressed.

The reactive surfactant is a surfactant having a functional group capable of reacting with a monomer component constituting the impact strength modifier. Examples of the functional group include a vinyl group, an epoxy group, and a hydroxyl group. Specific examples of the reactive surfactant include a polyoxyethylene alkyl ether having a functional group, a polyoxyethylene alkyl ether sulfate having a functional group, an alkyl fatty acid salt having a functional group, an alkyl phosphoric acid having a functional group, or Examples of such salts are generally available, and preferable examples include Kao Corporation, Latemul S-180, Lateml PD-104, Latemul PD-420, Laterum PD-430, or FP-manufactured by Toho Chemical. 120.
The content of the reactive surfactant in the impact strength modifier is usually 0.1 to 20 parts by mass, preferably 0.3 to 10 parts by mass, and more preferably 0 to 100 parts by mass of the graft polymer. .4-7 parts by mass.

The graft polymer comprises a rubber component and a graft component bonded to the rubber component. The rubber component can improve impact resistance, and the graft component can increase the dispersibility in the polyacetal resin and the recoverability during production.
Examples of the rubber component of the impact strength modifier include diene rubber, which is a polymer of diene monomer, acrylic rubber, which is a polymer of (meth) acrylic monomer, and silicone monomer. A composite rubber of a polymer and a polymer of a diene monomer or an acrylic monomer can be used. The type of the rubber component is appropriately selected according to the required performance. However, when a high toughness is required, those containing a diene monomer are preferable.

 The diene rubber preferably includes a butadiene monomer such as 1,3 butadiene as a diene monomer. In particular, when the total amount of the diene rubber is 100 parts by mass, 1,3 butadiene units are included. What is 30 parts by mass or more, preferably 60% by mass or more is preferable. When the amount of 1,3 butadiene is 60 parts by mass or more, the impact resistance imparting effect is more exhibited.

Examples of the (meth) acrylic monomer forming the acrylic rubber include, for example, methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, ethoxyethoxyethyl acrylate, methoxytripropylene glycol acrylate, hydroxyethyl acrylate, 4-hydroxybutyl acrylate, Examples thereof include lauryl methacrylate and stearyl methacrylate. Among these, butyl acrylate, propyl acrylate, 2-ethylhexyl acrylate and octyl acrylate are preferably used.
Further, other monomers copolymerizable with these may be copolymerized within a range not impairing impact resistance, specifically, within a range of 30% by mass or less. Examples of other monomers include aromatic alkenyl compounds such as styrene, α-methylstyrene, and vinyl toluene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; various vinyl compounds such as methacrylic acid-modified silicone and fluorine-containing vinyl compounds. Monomer.

  As the composite rubber, a silicone / acrylic composite rubber is preferable. Further, as the silicone / acrylic composite rubber, 1 to 99% by mass of the polyorganosiloxane component and 99 to 1% by mass of the polyalkyl (meth) acrylate rubber component cannot be separated. Thus, it is preferable to have a structure in which they are intertwined with each other and the total amount of the polyorganosiloxane component and the polyalkyl (meth) acrylate rubber component is 100% by mass.

 As the monomer constituting the polyorganosiloxane, for example, a diorganosiloxane monomer is used. Examples of the diorganosiloxane include 3-membered or more diorganosiloxane-based cyclics, and those having 3 to 7 members are particularly preferable. Specific examples include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. These may be used alone or in combination of two or more.

 In addition, for compounding with a vinyl monomer or the like, it is necessary to include a monomer component capable of reacting with them. The vinyl polymerizable functional group-containing siloxane is not particularly limited as long as it contains a vinyl polymerizable functional group and can be bonded to the diorganosiloxane via a siloxane bond, but considering the reactivity with the diorganosiloxane. Various alkoxysilane compounds containing a vinyl polymerizable functional group are preferred. Specifically, β-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylethoxydiethylsilane, γ-methacryloyloxypropylethoxydiethoxymethylsilane and δ-methacryloyloxybutyldiethoxymethylsilane and other methacryloyloxysilane, tetramethyltetravinylcyclotetrasiloxane and other vinylsiloxanes, p-vinylphenyldimethoxymethylsilane and other vinylphenylsilanes And γ-mercaptopropyldimethoxymethylsilane, γ-mercaptopropyltrimethoxysilane, etc. Script siloxane and the like are suitable. In addition, vinyl-polymerizable functional group containing siloxane may be used individually by 1 type, and may use 2 or more types together.

 The polyorganosiloxane may be copolymerized with a siloxane crosslinking agent. As the siloxane-based crosslinking agent, trifunctional or tetrafunctional silane-based crosslinking agents such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, and tetrabutoxysilane are preferably used.

Depending on the type of the functional group of the reactive surfactant, the rubber component may be copolymerized with a vinyl compound having a functional group capable of binding thereto.
Furthermore, the rubber component may be copolymerized with a crosslinking agent and / or a graft crossing agent as necessary.
Examples of the crosslinking agent include aromatic polyfunctional vinyl compounds such as divinylbenzene and divinyltoluene; dicarboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, propylene glycol dimethacrylate, and 1,3 butanediol diacrylate; Silicone such as methacryl group-modified silicone is suitable.
Examples of the grafting agent include: trimethacrylic acid ester; triacrylic acid ester; carboxylic acid allyl ester such as allyl acrylate and allyl methacrylate; di- or triallyl compounds such as diallyl phthalate, diallyl sebacate, and triallyl triazine; Allyl methacrylate, triallyl cyanurate, triallyl isocyanurate and the like are preferable. Allyl methacrylate can also be used as a crosslinking agent.
These crosslinking agents and graft crossing agents may be used alone or in combination of two or more.

The content of the crosslinking agent in the diene rubber may be appropriately determined according to the required level of stress whitening, but the impact resistance imparting effect can be achieved by the content being 10 parts by mass or less. Prevent decline.
In the acrylic rubber, the content of the crosslinking agent and / or graft crossing agent is preferably 20% by mass or less, more preferably in the range of 0.1 to 18% by mass, since the impact resistance imparting effect is not impaired. It is.

The rubber component preferably has a mass average particle diameter (d _w ) of 70 to 300 nm, more preferably 80 to 240 nm, since it does not impair other mechanical properties while increasing impact resistance.
If the mass average particle diameter (d _w ) is less than 80 nm, the impact resistance imparting effect may be reduced, and if it exceeds 300 nm, the stress whitening resistance may be deteriorated. Here, the mass average particle diameter (d _w ) of the rubber component can be measured by a known method. For example, it can be measured using a commercially available capillary particle size distribution meter.

  The rubber component is preferably produced by an emulsion polymerization method. When manufactured by the emulsion polymerization method, a latex-like rubber component is obtained, so that the graft component can be subsequently emulsion polymerized. The polymerization temperature during the polymerization is generally about 40 to 80 ° C., although it depends on the type of polymerization initiator.

As the monomer unit constituting the graft component, it is preferable to use a methacrylic acid ester, and if necessary, an aromatic vinyl compound is used, and if necessary, other copolymerizable vinyl-based compounds. It is preferable to use a monomer such as an acrylic ester or a vinyl cyanide compound in combination.
Specific examples of the methacrylic acid ester include methyl methacrylate and ethyl methacrylate.
Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, halogen, alkyl-substituted styrene and the like.
Specific examples of other copolymerizable vinyl monomers include acrylic acid alkyl esters such as ethyl acrylate and n-butyl acrylate; unsaturated nitriles such as acrylonitrile and methacrylonitrile; glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. Examples thereof include glycidyl group-containing vinyl monomers.

  To produce the impact strength modifier, in the impact strength modifier production process, first, the rubber component and the monomer constituting the graft component are mixed in the presence of the reactive surfactant, A polymerization initiator is added, and it heats and emulsion-polymerizes. Next, the impact strength modifier is recovered by removing water from the latex obtained by emulsion polymerization.

Examples of the polymerization initiator used in the emulsion polymerization include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; t-butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, Organic peroxides such as diisopropylbenzene hydroperoxide; azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile; the above compounds and sulfites, bisulfites, thiosulfates, first metal salts, sodium Examples include redox initiators combined with formaldehyde sulfoxylate, dextrose, and the like.
When adding an iron compound as needed during emulsion polymerization, the amount of the iron compound is preferably 10 ppm or less, and more preferably 5 ppm or less. This has the meaning of suppressing the decomposition of the polyacetal resin, and if it exceeds the above range, the polyacetal resin may be decomposed, which is not preferable.

 Furthermore, at the time of emulsion polymerization, a non-reactive surfactant such as naphthalene sulfonic acid formalin condensate or a dispersant such as polyoxyethylene alkyl ether may be added as necessary. In that case, the content of the non-reactive surfactant or dispersant in the impact strength modifier is usually 0.1 to 20 parts by weight, preferably 0.3 to 10 parts by weight with respect to 100 parts by weight of the graft polymer. It is added so that it becomes the range of a mass part, More preferably, it is 0.4-7 mass part. If the amount is less than 0.1 parts by mass, the emulsion polymerization stability during the production of the impact strength modifier may be impaired. If the amount exceeds 20 parts by mass, the dispersibility and impact resistance of the impact strength modifier may be impaired. May impair the performance, which is not preferable.

As a method for recovering the impact strength modifier, a known technique for removing water from the latex can be employed. For example, a coagulation method in which acid, base, etc. are added to the latex and aggregated, separated, washed and then dried and recovered as a powder, and the latex is cooled and frozen as it is, and when the emulsification ability is deactivated, separation, Examples thereof include a freeze coagulation method in which the particles are washed and dried and then recovered, and a spray recovery method in which the moisture of the latex is removed and recovered as it is using a spray recovery device.
The acid used in the coagulation method is preferably sulfuric acid or hydrochloric acid, and the salts are preferably calcium salt or magnesium salt. Aluminum salts are not preferred because they tend to promote the decomposition of the polyacetal resin.

The rubber component content in the impact strength modifier is preferably 50 to 95% by mass. When the amount is less than 50% by mass, the impact resistance may be insufficient. When the amount exceeds 95% by mass, dispersibility in the polyacetal resin is likely to be lowered, and recovery as a powder becomes difficult. There is.
When the rubber component is a composite rubber containing a polyorganosiloxane and a polyalkyl (meth) acrylate rubber, the content of the polyorganosiloxane in the impact strength modifier is 8 to 70% by mass, and the content of the composite rubber is 65. It is preferable that it is -90 mass%.

 The content of iron or ions thereof in the impact modifier is preferably 15 ppm or less, more preferably 10 ppm, and particularly preferably 8 ppm or less. If it exceeds 15 ppm, the decomposition of the polyacetal resin is likely to be manifested, and physical properties such as impact resistance tend to be deteriorated.

"Thermoplastic resin composition"
The thermoplastic resin composition of the present invention can be obtained by blending a predetermined amount of impact strength modifier with respect to the polyacetal resin in the blending step. There is no restriction | limiting in particular as that method, The well-known method generally used for preparation of a resin composition can be selected suitably. For example, a thermoplastic resin composition can be prepared by mixing a polyacetal resin and an impact strength modifier directly or in advance, and then kneading and pelletizing the mixture with a single or twin screw extruder.
In addition, as a method for molding the thermoplastic resin composition, a method of molding pellets prepared in the target composition as described above is suitable, but after preparing a plurality of types of pellets having different compositions, It is also possible to employ a method of mixing (diluting) at a predetermined ratio and subjecting to molding, and obtaining the target composition after molding. In preparing the pellets, it is preferable to pulverize a part or all of the polyacetal resin (A) as a substrate in advance in order to improve the dispersibility of the components to be blended therein.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. “Part” and “%” represent “part by mass” and “% by mass”, respectively, unless otherwise specified.

"Manufacture of impact strength modifiers (production examples)"
(Production Example 1) Impact strength modifier (1)
A pressure vessel equipped with a jacket and a stirrer was charged with a first monomer mixture for rubber components comprising the components shown in Table 1. While stirring the first monomer component for rubber component, the temperature was raised to 50 ° C., and 0.05 parts of “V-50” manufactured by Wako Pure Chemical Industries, Ltd. dissolved in 20 parts of ion-exchanged water was added to initiate polymerization. did. After the polymerization was started, the jacket was held at 60 ° C. for 90 minutes, the temperature in the container was adjusted to 60 ° C., and then 0.2 part of “V-50” manufactured by Wako Pure Chemical Industries, Ltd. dissolved in 20 parts of ion-exchanged water was added.
Subsequently, the second monomer mixture for rubber component shown in Table 1 was stirred at 10,000 rpm for 5 minutes with a homomixer, and dropped over 90 minutes for polymerization. The particle size of the rubber component obtained here was 150 nm.
Then, after holding at a jacket temperature of 60 ° C. for 90 minutes, a monomer mixture for graft component consisting of the components shown in Table 1 was prepared, and after dropping the monomer mixture for graft component over 40 minutes, The jacket temperature was maintained at 60 ° C. for 90 minutes to complete the polymerization.
The latex obtained was dissolved in 5 parts of calcium acetate, poured into 200 parts of ion-exchanged water adjusted to 70 ° C., and coagulated, followed by centrifugal dehydration. Next, the wet powder obtained by centrifugal dehydration was put into 200 parts of ion-exchanged water adjusted to 70 ° C., and the process of centrifugal dehydration again was performed for a total of 4 cycles. Thereafter, it was dried in a dryer at 60 ° C. for 48 hours to obtain a powdery impact strength modifier (1).

The particle size distribution was measured as follows.
A sample obtained by diluting the obtained latex with ion-exchanged water was used as a sample and measured using a CHDF2000 type particle size distribution meter manufactured by MATEC USA. The measurement conditions were standard conditions recommended by MATEC. That is, using a dedicated particle separation capillary cartridge and carrier liquid, the liquidity is almost neutral, the flow rate is 1.4 ml / min, the pressure is about 4000 psi, the temperature is 35 ° C., and the diluted latex sample has a concentration of about 3%. Measurements were made on 0.1 ml. As the standard particle size substance, a total of 12 monodispersed polystyrenes having a known particle size manufactured by DUKE Corporation in the range of 0.02 μm to 0.8 μm were used.

(Production Example 2) Impact strength modifier (2)
An impact strength modifier (2) having a rubber component particle size of 140 nm was obtained in the same manner as in Production Example 1 except that Kao Latemul PD-104 was used as the reactive surfactant in Production Example 1.

(Production Example 3) Impact strength modifier (3)
99.5 parts of 2-ethylhexyl acrylate and 0.2 parts of allyl methacrylate were mixed to obtain 100 parts of a (meth) acrylate monomer mixture.
Next, 100 parts of the above (meth) acrylate monomer mixture was added to 195 parts of ion-exchanged water in which 2 parts (solid content) of Kao Latemul PD-104, which is a reactive surfactant, was dissolved. After pre-stirring at 1,000 rpm, the mixture was emulsified and dispersed with a homogenizer under a pressure of 300 kg / cm ² to obtain a (meth) acrylate emulsion.
This emulsion was transferred to a separable flask equipped with a condenser and a stirring blade, and the temperature was raised while purging with nitrogen and mixing and stirring. When the temperature reached 50 ° C., 0.5 part of Wako Pure Chemical Industries Azo initiator V-50 was added. And 10 parts of ion-exchanged water were added. Thereafter, it was left for 5 hours to complete the polymerization, and an acrylic rubber (Q1) latex was obtained.
The polymerization rate of the obtained acrylic rubber (Q1) latex was 99.9%. The latex was coagulated and dried with ethanol to obtain a solid, extracted with toluene at 90 ° C. for 12 hours, and the gel content was measured to be 93.7%.
Next, 1.0 part of Kao Latemul PD-104 as a solid content was added to the resulting acrylic rubber (Q1) latex. This latex was collected so that the solid content of poly-2-ethylhexyl acrylate containing allyl methacrylate was 20 parts, and placed in a separable flask equipped with a stirrer so that the amount of ion-exchanged water in the system was 195 parts. Ion exchange water was added.

Next, 68 parts of n-butyl acrylate containing 2.0% of allyl methacrylate constituting the acrylic rubber (P1) component is charged and stirred for 10 minutes, and this mixed liquid is allowed to permeate the previously prepared acrylic rubber (Q1) particles. It was. After stirring for another 10 minutes, the atmosphere was replaced with nitrogen, the temperature inside the system was raised to 50 ° C., and a mixture of 0.5 part of Wako Pure Chemical Industries Azo initiator V-50 and 5 parts of ion-exchanged water was charged. The radical polymerization was started. Thereafter, the inner temperature was maintained at 70 ° C. for 2 hours to complete the polymerization, and a polyalkyl (meth) acrylate composite rubber latex comprising an acrylic rubber (P1) component and an acrylic rubber (Q1) component was obtained.
A part of this latex was sampled and the particle size distribution of the polyalkyl (meth) acrylate composite rubber was measured. The mass average particle diameter was 140 nm. The latex was dried to obtain a solid, extracted with toluene at 90 ° C. for 12 hours, and the gel content was measured and found to be 98.3%.
A monomer mixture containing 11.5 parts of methyl methacrylate and 0.5 part of butyl acrylate is dropped into the obtained polyalkyl (meth) acrylate composite rubber latex at 70 ° C. over 15 minutes, and then at 70 ° C. Holding for 4 hours, the graft polymerization onto the polyalkyl (meth) acrylate composite rubber was completed, and an acrylic rubber graft copolymer latex was obtained.
The latex obtained was dissolved in 5 parts of calcium acetate, poured into 200 parts of ion-exchanged water adjusted to 70 ° C., and coagulated, followed by centrifugal dehydration. Next, the wet powder obtained by centrifugal dehydration was put into 200 parts of ion-exchanged water adjusted to 70 ° C., and the process of centrifugal dehydration again was performed for a total of 4 cycles. Thereafter, it was dried in a dryer at 60 ° C. for 48 hours to obtain a powdery impact strength modifier (3).

(Production Example 4) Impact strength modifier (4)
After charging 0.5 parts (solid content) of Kao Latemul PD-104, which is a reactive surfactant, and 70 parts of ion-exchanged water into an autoclave, the first rubber component monomer shown in Table 2 is used. The mixture was charged, the temperature was raised, and when the temperature reached 43 ° C., the following redox initiator was added to start the reaction. Thereafter, the temperature was further raised to 65 ° C.
Redox initiator:
Ferrous sulfate 0.0008 parts Dextrose 0.2 parts Ion-exchanged water 5 parts Three hours after the start of polymerization, 1.5 parts (solid content) of Kao Latemul PD-104 and 75 parts of ion-exchanged water and reaction system In addition, 0.2 part of p-menthane hydroperoxide as an initiator was further added, and immediately after that, a second monomer mixture for rubber component of the components shown in Table 2 was continuously dropped over 8 hours. did.
After 14 hours from the start of polymerization, a butadiene rubber polymer (R1) latex was obtained. The mass average particle diameter (d _w ) of the butadiene rubber polymer (R1) latex was 120 nm. The conversion rate of the butadiene rubber polymer (R1) in the latex was 95.1%.
75 parts (solid content) of the butadiene rubber polymer (R1) obtained above was charged into a flask purged with nitrogen, and the internal temperature was maintained at 70 ° C. Also, 1.5 parts of Kato Latemul PD-104 and 0.6 parts of sodium formaldehyde sulfoxylate were charged.
Subsequently, the monomer mixture for graft components of the components shown in Table 2 was dropped over 1 hour, and then held for 1 hour. The amount of cumene hydroxy peroxide added was 0.3% with respect to 100% of the total amount of graft monomers.
After completion of the polymerization reaction, a graft copolymer latex was obtained.
The latex obtained was dissolved in 5 parts of calcium acetate, poured into 200 parts of ion-exchanged water adjusted to 60 ° C., and coagulated, followed by centrifugal dehydration. Next, the wet powder obtained by centrifugal dehydration was put into 200 parts of ion-exchanged water adjusted to 70 ° C., and the process of centrifugal dehydration again was performed for a total of 4 cycles. Thereafter, it was dried in a dryer at 60 ° C. for 48 hours to obtain a powdery impact strength modifier (4).

(Production Example 5) Impact strength modifier (5)
In Production Example 4, rubber component particles were produced in the same manner as in Production Example 4 except that an ammonia neutralized product of Toho Chemical's reactive surfactant FP-120 was used instead of the reactive surfactant Latemul PD-104. An impact strength modifier (5) having a diameter of 130 nm was obtained.

(Production Example 6) Impact strength modifier (6)
In Production Example 1, 0.5 parts of sodium alkylbenzene sulfonate was used in place of 1.0 part of the reactive surfactant Latemulu S-180 in the monomer mixture for the first rubber component. The particle size of the rubber component was the same as in Production Example 1 except that 2.0 parts of sodium alkylbenzene sulfonate was used instead of 2.0 parts of the reactive surfactant Latemul S-180 in the monomer mixture. A 150 nm powdery impact strength modifier (6) was obtained.

"Polyacetal resin"
A mixture of trioxane and a small amount of 1,3-dioxolane (comonomer) is polymerized in the presence of boron trifluoride etherate (catalyst) to give 0.75%, 1.00% and 1% oxyethylene groups. Three types of copolymers of 50% by weight were prepared. After the polymerization, the catalyst was deactivated with triethylamine (deactivator), and further pelletized through a terminal stabilization step.

(Examples 1-5, Comparative Example 1)
In the proportion shown in Table 3, 78 parts of polyacetal resin and 22 parts of impact strength modifier were blended and pelletized with a TEM35B twin screw extruder manufactured by Toshiba Machine to obtain pellets of a thermoplastic resin composition. Subsequently, in order to perform various evaluation tests, the obtained pellets of the thermoplastic resin composition were injection molded under normal conditions using a SAV60 type injection molding machine manufactured by Sanjo Kikai to prepare a test piece.

(Evaluation test)
The obtained thermoplastic resin composition was evaluated as follows. The results are shown in Table 3.
1) Izod impact strength The Izod impact strength of a test piece with a sample thickness of 1/8 inch and a notch was measured at 23 ° C. according to ASTM D256.
2) Flexural modulus The flexural modulus of a test piece having a sample thickness of ¼ inch was measured at 23 ° C. according to ASTM D790.
3) Resin decomposability test A Brabender plastmill equipped with a W50E type biaxial head was adjusted to 200 ° C., and 60 g of pellets of the thermoplastic resin composition were kneaded for 5 minutes. At that time, the degree of decomposition was evaluated in three stages, ◯, Δ, and ×, based on the odor and gas generation status. ○ indicates that there is almost no odor and gas is not generated, and △ indicates that there is a slight odor or gas is generated. X indicates a very strong odor and gas is generated, and ◯ is the best.

(result)
In the examples using the reactive surfactant, the decomposition of the polyacetal resin was suppressed, and good impact resistance was exhibited. In particular, Examples 4 and 5 in which the rubber component of the impact strength modifier is a diene rubber exhibited very excellent impact resistance.
On the other hand, in the comparative examples in which no reactive surfactant was used, the polyacetal resin was decomposed and the impact resistance was low.

  The thermoplastic resin composition of the present invention is suitably used for resin gears and mechanical parts used for OA equipment, information equipment, home appliances, automobiles, clothing, stationery, sundries, building materials, and the like.

Claims (2)

Polyacetal resin,
A thermoplastic resin composition comprising a surfactant having reactivity and an impact strength modifier including a graft polymer in which at least a part of the surfactant is chemically bonded. An impact strength modifier manufacturing process for obtaining an impact strength modifier by removing water after emulsion polymerization of a monomer to a rubber component in the presence of a reactive surfactant;
A method for producing a thermoplastic resin composition, comprising a blending step of blending the impact strength modifier and a polyacetal resin.