JP3290290B2 - Thermoplastic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition containing polyacetal and polystyrene resin as main components. More specifically, a polyacetal and a polystyrene-based resin are the main components, and a polymer having a hydroxyl group and a polyfunctional isocyanate are added as compatibilizers. The molded product has a good surface condition, good abrasion resistance and molding shrinkage. The present invention relates to a thermoplastic resin composition having a low ratio.

[0002]

BACKGROUND OF THE INVENTION Polyacetals have well-balanced mechanical and electrical properties,
Because it has heat resistance, chemical resistance, friction and wear characteristics, and also has excellent fatigue resistance as a plastic material,
It is used in a very wide range of fields as a representative engineering plastics. However, with the expansion of application fields, the required performance for resins tends to be more and more advanced, and such demands include reduction of molding shrinkage, improvement of printability and plating property. In other words, polyacetal has a high molding shrinkage due to its high crystallinity, and also has problems such as shrinkage or warpage of molded products in the molding of precision parts, thin-walled parts, and large-sized parts. Considering mold design is required, and improvement of these disadvantages is often desired. Further, polyacetal belongs to an excellent class with respect to friction and wear characteristics, but further improvement is often desired. On the other hand, polystyrene resins are used in a wide range of fields because of their low molding shrinkage, good printability, good plating properties, and low cost, but their chemical resistance and abrasion resistance are low. Has been limited. Generally, as a method for improving various physical properties of a polyacetal resin, blending of another resin has been attempted. The blending of the polystyrene resin is one of them, for example, there are proposals in Japanese Patent Publication No. 44-946 and Japanese Patent Application Laid-Open No. 64-38463, but the former is intended for fibrous materials, According to the study of the present inventors, the polymer mixture obtained by this description is not practically useful because when used for molding, layer separation and delamination phenomena are strongly exhibited. In addition, the latter shows that the use of a specific polystyrene resin having a high viscosity is effective to solve such a problem, but it is still not sufficient, and particularly causes an increase in the viscosity of the composition.
There is a problem in molding. As described above, it is expected that each of the disadvantages will be improved by blending the polyacetal resin with the polystyrene resin, but simply blending causes strong layer separation and delamination during molding as described above. It has no practical value.

[0003]

DISCLOSURE OF THE INVENTION In view of the above problems, the present inventors have found that in a polymer blend of a polyacetal resin and a thermoplastic polystyrene resin, an injection-molded product based on poor dispersibility of both and poor adhesion between resin layers. The appearance of a striped phase-separated structure on the surface of the surface, the occurrence of surface delamination due to friction, and the loss of friction and wear characteristics, one of the characteristics of polyacetal resin, are eliminated, and the dispersibility is improved. As a result of earnestly studying for the purpose of obtaining a thermoplastic resin composition in which the surface state of the product is uniform and smooth, excellent in friction and wear characteristics, and improved in shrinkage ratio during molding, warpage, printability, plating properties, etc., Hydroxyl-containing styrene and / or
Alternatively, it has been found that the above-mentioned problems can be solved and a good polyacetal resin molded article can be obtained by blending a specific amount of a (co) polymer composed of a (meth) acrylate and a polyfunctional isocyanate. This has led to the invention. That is, the present invention relates to a composition comprising a polyacetal resin (A) and a thermoplastic polystyrene resin (B), a polystyrene resin containing a hydroxyl group (C-1) as a component (C), and a poly (meta) resin containing a hydroxyl group. A) an acrylic acid ester, a thermoplastic resin composition containing a polymer selected from a copolymer comprising a (meth) acrylic acid ester having a hydroxyl group and styrene, and (C-2) a polyfunctional isocyanate, (A) / (B) weight ratio of 5/95 to 95/5, (C)
The amount of component added is (A) + (B) 1 to 100 parts by weight of the total amount.
The present invention relates to a thermoplastic resin composition characterized in that the amount is from 30 to 30 parts by weight.

[0004] In the composition of the present invention, the polyacetal resin used as the component (A) is an oxymethylene group.
In polymer compound and (-CH ₂ O-) the main structural units, polyacetal homopolymers or oxymethylene group as the main repeating unit, other structural units in addition to this, for example ethylene oxide, 1,3 - dioxolane, Copolymers containing a small amount of comonomer units such as 1,4-butanediol and formal, terpolymers, and block copolymers may be used, and molecules having not only linear but also branched or crosslinked structures may be used. It may be a known modified polyoxymethylene into which another organic group is introduced.
The degree of polymerization and the like are not particularly limited as long as they have moldability (for example, a melt flow value (MFR) at 190 ° C. under a load of 2160 g of 1.0 to 100).

[0005] Next, as is known, the thermoplastic polystyrene resin of the component (B) used in the present invention is obtained by a radical polymerization reaction or an ionic polymerization reaction mainly using styrene. Any of those obtained by polymerization, solution polymerization, suspension polymerization, emulsion polymerization and the like can be used. In addition to polystyrene, the polystyrene resin used as the component (B) of the present invention is mainly composed of styrene, and other monomers such as vinyl compounds and diene compounds are copolymerized, or these are graft-polymerized to a rubber component. Modified ones (ABS, MBS, high impact polystyrene (HIPS), etc.) may be used. Especially polystyrene,
Poly-α-methylstyrene or those mainly,
Copolymerization with acrylic acid ester, methacrylic acid ester, acrylonitrile, butadiene, chlorinated ethylene and the like is preferably used. The component (B) also includes a hydrogenated product of a copolymer of an aromatic hydrocarbon such as styrene and a conjugated diene. Copolymer of aromatic hydrocarbon and conjugated diene, for example, styrene-butadiene block or random copolymer, styrene-ethylene / propylene-styrene copolymer obtained by hydrogenating styrene-isoprene block random copolymer, styrene-ethylene -Propylene-styrene copolymer etc. are mentioned.

[0006] Of the component (C) used in the present invention, (C-1)
The hydroxyl group-containing polymer used as a component has a repeating unit of styrene and / or (meth) acrylic acid ester, specifically, a polystyrene resin containing a hydroxyl group, and a poly (meth) acrylic acid containing a hydroxyl group. It is a polymer selected from a copolymer consisting of an ester, a hydroxyl group-containing (meth) acrylate and styrene. In addition, these polymers may be copolymerized with vinyl compounds other than styrene, monomers such as diene compounds, acrylates, methacrylates, acrylonitrile, butadiene, chlorinated ethylene, etc., so long as the properties are not significantly impaired. The polymer is also included. In order to prepare a hydroxyl group-containing polymer, these monomers are copolymerized with a hydroxyl group-containing monomer such as 2-hydroxyethyl methacrylate. Oxidation of the saturated double bond, modification by phenol addition using the Friedel-Crafts reaction, polymerization using an initiator containing a hydroxyl group, copolymerization of a monomer having a carboxylic acid such as (meth) acrylic acid. There is a method of introducing a hydroxyl group by reducing the obtained polymer. As the polyfunctional isocyanate to be added as the component (C-2), difunctional, trifunctional or higher functional isocyanates are used. Specific examples thereof include methylene diisocyanate, toluene 2,4-diisocyanate, isophorone diisocyanate and trimer of isophorone diisocyanate. And an isocyanate group obtained by reacting an amino group-containing polymer with phosgene.

In the present invention, the mixing ratio of the component (A) and the component (B) can be arbitrarily selected so that the weight ratio of (A) / (B) is 5/95 to 95/5. Increase the compounding ratio of component (A) if you want to give more weight to friction / wear resistance and chemical resistance, and mix component (B) if you want to reduce the specific gravity or give more weight to moldability. What is necessary is just to increase a ratio. The amount of the component (C) added is 1 to 100 parts by weight of the total of the components (A) and (B).
~ 30 parts by weight. When the amount is less than 1 part by weight, the compatibilizing effect is insufficient, and when the amount is more than 30 parts by weight, the resin composition becomes expensive, and the melt viscosity is increased, and the processability is reduced. . The ratio of the compounding amount of the component (C-1) to the compounding amount of the polyfunctional isocyanate of the component (C-2) is 40/60 to 40/60.
It is preferably 95/5, particularly preferably 50/50 to 90/10. Outside this range, if the component (C-2) is too large relative to the component (C-1), the resulting resin composition becomes brittle due to crosslinking of the component (C-1). In addition, (C
-2) When the amount of the component is small, the reaction with the modified polymer hardly occurs, which causes defects such as surface layer peeling.

As described above, if the polyacetal and the thermoplastic polystyrene resin are simply melt-kneaded, the dispersed resin phase appears as a striped phase-separated structure on the surface of the injection-molded product, and the surface layer is separated by friction. . This is because the dispersed resin phase is deformed by high shear stress generated near the surface layer during injection molding to form a layered structure, and a surface layer peeling phenomenon occurs due to poor adhesion between the polystyrene phase and the polyacetal phase.
That is, in order to improve the adhesiveness of both phases, by mixing a hydroxyl group-containing polymer and a polyfunctional isocyanate, not only the adhesiveness of both phases is improved to prevent surface layer peeling, but also the molded article It is understood that this has the effect of improving the surface condition and also improving the friction and wear characteristics.

[0009] The thermoplastic resin composition of the present invention is characterized in that
In addition to the components (A), (B) and (C), a small amount of a catalyst for promoting the reaction between the isocyanate and the hydroxyl group-containing polymer may be added. Examples of such a catalyst include tin catalysts such as dibutyltin dilaurate, amines such as pyridine, and metal salts of carboxylic acids such as zinc stearate and calcium stearate. The amount of these reaction catalysts added is (A) +
(B) 0.001 to 1 part by weight per 100 parts by weight is preferred.

In addition, mechanical strength, heat resistance, dimensional stability,
Fibrous materials such as glass fiber and carbon fiber and other fillers can be blended according to the purpose such as electrical properties.

The composition of the present invention may contain an antioxidant, a heat stabilizer, an ultraviolet absorber, a coloring agent, a release agent and other usual additives. In addition, a small amount of a thermoplastic resin can be added as an auxiliary.

Although the preparation of the thermoplastic resin composition of the present invention can be carried out by various known methods, at least (A), (B),
(C) It is necessary to melt and knead in the presence of three components,
Other components may be mixed and mixed simultaneously, or may be added separately. Specifically, (A) component polyacetal and
The master pellets prepared by melt-kneading the hydroxyl group-containing polymer (C) and the polyfunctional isocyanate are mixed with the master pellets (A) and (B).
After being supplied to the compound and melt-kneaded into pellets, the pellets may be subjected to molding. The treatment temperature is a temperature 5 to 100 ° C. higher than the temperature at which the resin component melts or softens, and is particularly preferably a temperature 10 to 60 ° C. higher than the melting point. If the temperature is too high, decomposition or an abnormal reaction is likely to occur, which is not preferable.

[0013]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Examples 1 to 3 As shown in Table 1, (A) polyacetal resin (manufactured by Polyplastics, Duracon M90-44), (B) polystyrene (Nippon Steel Chemical G12-55), (C-1) hydroxyl group-containing polystyrene (See Reference Example below), (C-2) isophorone diisocyanate trimer (trifunctional isocyanate, Vestenat IPDI-T1890 manufactured by Huls) was mixed at the ratio (weight) shown in Table 1, and at a set temperature of 190 ° C. Using a twin-screw extruder having an inner diameter of 30 mm, the mixture was melt-kneaded at a screw rotation speed of 100 rpm and pelletized. Next, the pellets were heated at 200 ° C. by an injection molding machine.
At a set temperature to prepare a test piece, and the following mechanical properties were evaluated. Tensile strength; in accordance with ASTM D638 Surface peeling test: An adhesive tape was stuck to the surface of a tensile test piece, which was instantaneously peeled off, and the presence or absence of surface peeling of the molded piece was visually judged. Shrinkage rate: The dimension of the ASTM tensile test specimen in a certain direction was accurately measured, and the difference (%) from the corresponding metal mold dimension was used as the shrinkage rate. Friction and wear test: The specific wear amount on steel S55C was measured by a Suzuki-type friction and wear tester. The results are shown in Table 1.

The hydroxyl group-containing polymer used in the examples was produced as follows. Reference Example 1 Preparation of hydroxyl group-containing polystyrene (PS-OH-1) In a reaction vessel equipped with a stirrer and a condenser, 40 parts by weight of toluene and 60 parts by weight of monomers (styrene / 2-hydroxyethyl methacrylate = 95/5) were introduced in a nitrogen stream. (Mol ratio)), di-
0.06 parts by weight of t-butyl peroxide and 0.07 parts by weight of t-butyl peroxy-2-ethylhexanoate were charged, and stirring was continued at 110 ° C. for 3 hours. After cooling to room temperature, the reaction solution was poured into a large amount of methanol, and the precipitated polymer was repeatedly dried and reprecipitated to obtain a styrene resin (PS-
OH-1) was obtained. ^The styrene / 2-hydroxyethyl methacrylate calculated from the ¹ H-NMR spectrum was in agreement with the charging ratio, and a resin having a glass transition point at 80 ° C. was obtained. Reference Example 2 Hydroxyl-containing polymethyl methacrylate (PMMA
Preparation of —OH) In a reaction vessel equipped with a stirrer and a condenser, 40 parts by weight of toluene and 60 parts by weight of monomer (methyl methacrylate / 2-hydroxyethyl methacrylate = 95/5 (mol
Ratio)), 0.06 parts by weight of di-t-butyl peroxide, t
-Butyl peroxy-2-ethylhexanoate (0.07 parts by weight) was charged, and stirring was continued at 110 ° C for 3 hours. After cooling to room temperature, the reaction solution was poured into a large amount of methanol, and the precipitated polymer was repeatedly dried and reprecipitated to obtain a methyl methacrylate resin (PMMA-OH). Methyl methacrylate / 2-hydroxyethyl methacrylate calculated from the ¹ H-NMR spectrum was in agreement with the charged ratio. Reference Example 3 Preparation of hydroxyl group-containing polystyrene (PS-OH-2) In a reaction vessel equipped with a stirrer and a condenser, 40 parts by weight of toluene and 60 parts by weight of monomer (styrene / polycaprolactone oligomer = 95/5 (molar ratio) )), Di-t-
Butyl peroxide 0.06 parts by weight, t-butyl peroxy-2-ethylhexanoate 0.07 parts by weight,
Stirring was continued at 0 ° C. for 3 hours. The polycaprolactone oligomer has a structure in which a caprolactone dimer is bonded to a hydroxyl group of 2-hydroxyethyl methacrylate, and Placcel FM-2 manufactured by Daicel Chemical Industries, Ltd. was used. After cooling to room temperature, the reaction solution was poured into a large amount of methanol, and the precipitated polymer was repeatedly dried and reprecipitated to obtain a styrene resin (PS-OH-2). ^The styrene / polycaprolactone oligomer calculated from the ¹ H-NMR spectrum was consistent with the charged ratio. Reference Example 4 Preparation of Hydroxyl Group-Containing Polystyrene (PS-OH-3) In a reaction vessel equipped with a stirrer and a condenser, 40 parts by weight of toluene, 60 parts by weight of styrene monomer, and 2,2, a radical initiator having a hydroxyl group, were introduced in a nitrogen stream. '-Azobis [2-methyl-N (2-hydroxyethylpropionamide)] was charged in an amount of 0.06 part by weight, and stirring was continued for 3 hours at 110 ° C. After cooling to room temperature, the reaction solution was poured into a large amount of methanol. The precipitated polymer was repeatedly dried and reprecipitated to obtain a styrene resin (PS-OH-3).

Comparative Examples 1 to 7 As shown in Table 1, polyacetal resin alone, polystyrene resin alone, two-component system of polyacetal and polystyrene resin, and (C-1) or (C- When 2) was compounded alone, a composition was prepared in the same manner as in Examples 1 to 3, molded, and evaluated. The results are shown in Table 1.

[0016]

[Table 1]

Examples 4 to 9, Comparative Examples 1, 8 to 13 The polystyrene resin in Examples 1 to 3 and Comparative Examples 1 to 7 was changed to a styrene-acrylonitrile copolymer (AS).
(C-1) In addition to PS-OH-2, PAS-OH-1 and PS-
A composition was prepared in the same manner except that OH-3 and PMMA-OH were used, molded and evaluated. In addition, Sebian NO10 (AN / St = 27/73) manufactured by Daicel Chemical Industries, Ltd. was used as the AS resin. The results are shown in Table 2.

[0018]

[Table 2]

Examples 10-13, Comparative Examples 1, 14-19 Compositions were prepared, molded and evaluated in the same manner as in the above Examples and Comparative Examples, except that the component (B) was replaced with ABS resin. . (C
-1) PS-OH-2 and PMMA-OH were used as components. The results are shown in Table 3. The ABS resin used was Sebian V720 (MFR = 5, AN / St = 26/74, butadiene content 16%) manufactured by Daicel Chemical Industries, Ltd.

[0020]

[Table 3]

[0021]

As is clear from the above description and the examples, the composition of the present invention is obtained by peeling off the surface of a molded article due to poor dispersibility, as seen in a conventional blend of polyacetal and polystyrene resin. In addition, it is excellent in friction and wear characteristics, and has a low shrinkage ratio during molding. It is also effective for improving the dimensional accuracy of molded products, and its use is expected to expand.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // (C08L 25/04 (C08L 25/04 59:00 59:00 75:04) 75:04) (C08L 59/00 (C08L 59 / 00 25:04 25:04 75:04) 75:04) 25:04 25:04 59:00 59:00 (56) References JP-A-63-182328 (JP, A) JP-A-3-47819 ( JP, A) JP-A-3-188152 (JP, A) JP-A-4-68069 (JP, A) JP-A-5-255570 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) C08L 25/04-25/14 C08G 18/62 C08J 5/00 C08L 59/00-59/04 C08L 75/04-75/16

Claims (4)

(57) [Claims] 1. A composition comprising a polyacetal resin (A) and a thermoplastic polystyrene resin (B) as a component (C)
(C-1) a polymer selected from a polystyrene resin containing a hydroxyl group, a poly (meth) acrylate ester containing a hydroxyl group, a copolymer composed of a styrene ester containing a (meth) acrylate ester containing a hydroxyl group, and ( C-2) a thermoplastic resin composition to which a polyfunctional isocyanate is added,
The weight ratio of (A) / (B) is 5/95 to 95/5, and the amount of component (C) added is 1 to 30 with respect to 100 parts by weight of the total amount of (A) + (B).
A thermoplastic resin composition characterized by being in parts by weight. 2. The thermoplastic resin composition according to claim 1, further comprising 0.001 to 1 part by weight of a reaction catalyst for a hydroxyl group and an isocyanate group per 100 parts by weight of (A) + (B). 3. The method according to claim 1, wherein a filler is further added.
The thermoplastic resin composition according to the above. 4. A molded article obtained by molding the thermoplastic resin composition according to claim 1.