JPH06100758A - Polyacetal resin composition - Google Patents

Abstract

PURPOSE:To provide a polyacetal resin having improved fluidity without lowering the impact resistance. CONSTITUTION:The objective polyacetal resin composition is produced by compounding a polyacetal resin with (A) 1-40wt.% (based on the total composition) of a core-shell polymer having a core composed of a rubbery polymer and a shell composed of a glassy polymer and (B) 0.01-1wt.% of a polyhydric alcohol fatty acid ester compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal resin composition, and more particularly to a polyacetal resin composition having excellent impact resistance and excellent in-mold flow characteristics, and a molded product thereof.

[0002]

2. Description of the Related Art As is well known, a polyacetal resin is an engineering material having excellent physical properties such as mechanical properties and electrical properties, or chemical properties such as chemical resistance and heat resistance. Recently, it has been used as a resin in a very wide range of fields. However, with the expansion of fields in which polyacetal resins are used, further improvement in properties as materials has been required. As an example of such a requirement, for example, a clip for adhering or locking an article or a component or the like to a mating material by utilizing elastic repulsive force in an automobile or the like has high impact resistance in a wide temperature range. In addition, complicated shapes, cost reduction,
Improvement in fluidity is required for thinning due to weight reduction. By the way, as one of the means for improving the impact resistance of polyacetal resin, conventionally, a thermoplastic polyurethane resin is added and compounded (for example, JP-A-59-145243 and JP-A-61-19652), an acrylic resin. Addition of multiphase interpolymers (for example, JP-A-59-136343) has been proposed. However, these conventionally proposed methods provide a polyacetal resin composition having desirable properties in terms of impact resistance, but the former compounding of thermoplastic polyurethane results in a strong elongation of the welded part of the molded article. There is a problem that the appearance of the molded product is remarkably impaired by the phenomenon that the polyacetal resin and the polyurethane are separated from each other on the surface of the molded product, resulting in a remarkable decrease. In the case of the latter compounding of the acrylic multiphase interpolymer, special blending conditions are required, and a sufficiently stable polyacetal resin composition has not been obtained under ordinary blending conditions. For the purpose of solving the above-mentioned problems, addition and blending of various core-shell polymers have been proposed, and a composition having an improved strength and elongation at the weld part has been obtained. However, in general, when such a core-shell polymer is added to a polyacetal resin, there is a problem that the melt viscosity is remarkably increased and the fluidity in the mold is greatly reduced, and its improvement has been desired.

[0003]

Means for Solving the Problems As a result of intensive studies to obtain a polyacetal resin composition which does not have the above problems, the present inventors have found that a specific fatty acid ester compound is used in combination with a core-shell polymer in a polyacetal resin. The present inventors have found that the above is effective for achieving the intended purpose, and have completed the present invention. That is, the present invention, relative to the total composition, (A) 1-40 wt% core-shell polymer having a rubbery polymer core and a glassy polymer shell, (B) polyhydric alcohol fatty acid ester compound 0.01
The present invention relates to a polyacetal resin composition containing about 10% by weight.

The constituent components of the present invention will be described in detail below. First, the polyacetal resin used in the present invention is a polymer compound having an oxymethylene group (-CH ₂ O-) as a main constituent unit, and a polyoxymethylene homopolymer,
It may be a copolymer, terpolymer or block copolymer having a small amount of other constitutional units in addition to the oxymethylene group, and the molecule may have not only a linear structure but also a branched or crosslinked structure. The degree of polymerization is also not particularly limited, but the melt index at 190 ° C is 0.1
Those having -50 g / 10 min, especially 5-50 g / 10 min are preferred. If the melt index is less than 0.1 g / 10 minutes, general injection molding is difficult, and if it exceeds 50 g / 10 minutes, the impact resistance may be extremely poor.

The (B) core-shell polymer used in the present invention can be prepared by a known method, or a commercially available product can be used. A typical example is the Acryloid KM330 from Rohm and Haas and
KM653, Kureha Chemical's Paraloid KCA-102 and KCA-
301, Staphyroid PO-0270 of Takeda Pharmaceutical Co., Ltd.,
Kanae Ace FM of Kanegafuchi Chemical Industry Co., Ltd., Metabrene C-102, E-901, W-800, S-2001 etc. of Mitsubishi Rayon Co., Ltd. Among such core-shell polymers, preferred are core-shell polymers having a rubbery polymer core and a glassy polymer shell containing methyl methacrylate as a main component, and particularly a core-shell polymer in which anions are not substantially detected. In a polyacetal resin composition mixed with a core-shell polymer in which an anion is detected, the polyacetal may decompose and deteriorate during melting. Here, the core-shell polymer in which an anion is not substantially detected means a core-shell polymer in which an anion is not detected by a usual qualitative test of anion. For example, as a measuring method, 5 g of the sample (core-shell polymer) is weighed in a 50 ml Erlenmeyer flask, 20 ml of ion-exchanged water is added, the mixture is stirred with a magnetic stirrer for 3 hours, and then the filtrate filtered with No. 5 C filter paper is divided into two parts. Then, 0.5 ml of 1% barium chloride aqueous solution is added to one of them, and turbidity is comparatively observed (sulfuric acid ion qualitative test). Also, the same treatment is performed, and 0.1 N silver nitrate aqueous solution is used instead of 1% barium chloride aqueous solution The presence of anions can be confirmed by a method of comparing and observing the occurrence of turbidity (a qualitative test for halogen ions). A core-shell polymer in which these anions are not present is preferably used.

The core-shell polymer preferably used in the present invention is one obtained by emulsion polymerization using a nonionic surfactant and a polymerization initiator in which the radicals generated are neutral. The emulsion polymerization can be carried out, for example, using the following surfactants and polymerization initiators. As the nonionic surfactant, polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, ether type such as polyoxyethylene lauryl ether, ester type such as polyoxyethylene monostearate,
Most widely used nonionic surfactants such as sorbitan ester type such as polyoxyethylene sorbitan monolaurate and block polymer type such as polyoxyethylene polyoxypropylene block copolymer can be used. The amount of addition is appropriately selected according to the particle stabilizing ability of the surfactant.

As the polymerization initiator, azo-based polymerization initiators such as azobisisobutyronitrile, dimethyl 2,2'-azobisisobutyrate and 2,2'-azobis (2-aminopropane) dihydrochloride, cumene hydro Peroxide-based polymerization initiators such as peroxide, diisopropylbenzene hydroperoxide and hydrogen peroxide may be used alone or in combination of two or more. When emulsion polymerization is carried out in such a reaction system using a surfactant containing no anion and a polymerization initiator other than persulfate, the obtained core-shell polymer becomes substantially free of anion. The polyacetal resin composition using such a core-shell polymer that does not substantially contain anions has excellent impact resistance. The core-shell polymer in the present invention can be obtained by a continuous multi-step emulsion polymerization method in which the polymer of the previous step is sequentially coated with the polymer of the latter step, so-called seed emulsion polymerization method. At the time of particle generation polymerization, it is preferable to start the emulsion polymerization reaction by adding a monomer, a surfactant and water to a reactor, and then adding a polymerization initiator. The first stage polymerization is a reaction that forms a rubbery polymer. Examples of the monomer constituting the rubbery polymer include a conjugated diene or an alkyl group having 2 to 2 carbon atoms.
Examples thereof include alkyl acrylates of No. 8 and mixtures thereof. These monomers are polymerized to form a rubber-like polymer having a glass transition temperature of -30 ° C or lower. Examples of such conjugated dienes include butadiene, isoprene, chloroprene, and the like, but butadiene is particularly preferably used. Examples of the alkyl acrylate having an alkyl group having 2 to 8 carbon atoms include ethyl acrylate, propyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc., but butyl acrylate is particularly preferably used. In the first-stage polymerization, monomers copolymerizable with conjugated dienes and alkyl acrylates, for example, styrene, vinyltoluene, aromatic vinyl such as α-methylstyrene, aromatic vinylidene, acrylonitrile, methacrylonitrile, and cyanation It is also possible to copolymerize vinyl, vinylidene cyanide, alkyl methacrylate such as methyl methacrylate and butyl methacrylate. If the first stage polymerization does not contain conjugated dienes, or if it contains conjugated dienes and is 20% by weight or less of the total amount of monomers in the first stage, use a small amount of crosslinkable monomer and grafting monomer. It is possible to obtain a polymer having higher impact resistance. Examples of the crosslinkable monomer include aromatic divinyl monomers such as divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, hexanediol diacrylate, hexanediol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate. Methacrylate, trimethylol propane diacrylate, trimethylol propane dimethacrylate, trimethylol propane triacrylate, trimethylol propane trimethacrylate and the like alkane polyol polyacrylate or alkane polyol polymethacrylate can be mentioned,
In particular, butylene glycol diacrylate and hexanediol diacrylate are preferably used. Examples of the grafting monomer include unsaturated carboxylic acid allyl esters such as allyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate and diallyl itaconate, and allyl methacrylate is particularly preferably used. Such a crosslinkable monomer and a grafting monomer are used in an amount of 0 to 5% by weight, preferably 0.1 to 2% by weight, based on the total amount of the first stage monomers. The rubbery polymer core preferably ranges from 50 to 90% by weight of the total core-shell polymer.
When the core is less than this weight range or more than this weight range, the effect of improving impact resistance of the resin composition obtained by melt-mixing the produced core-shell polymer may not be sufficient. Also, the glass transition temperature of the core is -30
If it is higher than 0 ° C, the effect of improving low temperature impact resistance may not be sufficient. A glassy polymer is formed in the outermost shell phase (shell phase). Examples of the monomer constituting the glassy polymer include methyl methacrylate and a monomer copolymerizable with methyl methacrylate. These monomers are methyl methacrylate alone or a mixture of monomers copolymerizable with methyl methacrylate, and form a glassy polymer having a glass transition temperature of 60 ° C. or higher. Examples of monomers copolymerizable with methyl methacrylate include alkyl acrylates such as ethyl acrylate and butyl acrylate, ethyl methacrylate,
Alkyl methacrylate such as butyl methacrylate, styrene, vinyltoluene, aromatic vinyl such as α-methylstyrene, vinylidene aromatic, vinyl cyanide such as acrylonitrile and methacrylonitrile, vinyl polymerizable monomers such as vinylidene cyanide. I can, but
Particularly preferably, ethyl acrylate, styrene, acrylonitrile and the like are used. The outermost shell phase is preferably in the range of 10 to 50% by weight based on the whole core-shell polymer. When the outermost shell phase is less than or more than this weight range, the effect of improving the impact resistance of the resin composition obtained by melt mixing the resulting core-shell polymer may not be sufficient.

Further, an intermediate phase may be present between the first stage and the final polymerized phase. For example, polymerized monomers having functional groups such as glycidyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, etc., polymerized monomers that form glassy polymers such as methyl methacrylate, polymerized monomers that form rubbery polymers such as butyl acrylate, etc. The intermediate phase is formed by seed emulsion polymerizing. Such an intermediate phase can be variously selected depending on the desired properties of the core-shell polymer. Further, the polymerization ratio may be appropriately selected depending on the monomer used. For example, when the glassy polymer is used as the intermediate phase, its polymerization rate may be calculated as a part of the shell, and in the case of a rubbery polymer, it may be calculated as a part of the core.

The structure of the core-shell polymer having such an intermediate phase has, for example, a multi-layered structure in which another layer is present between the core and the shell, or the intermediate phase has a fine granular structure in the core. One that has a salami structure that is dispersed. In a more extreme case of a core-shell polymer having a salami structure, the mesophase to be dispersed may form a new core at the center of the core. The core-shell polymer having such a structure may occur when a monomer represented by styrene is used as a monomer constituting the mesophase. In addition, when a core-shell polymer having an intermediate phase is used, in addition to improving impact resistance, the flexural modulus is improved, the heat deformation temperature is increased, the appearance (surface peeling and pearl luster is suppressed, and the change in color tone due to the change in the refractive index). ) Is also improved. In the present invention, the amount of the (A) core-shell polymer added is 1 to 40% by weight, preferably 5 to 40% by weight, based on the total composition. If the addition amount of the core-shell polymer is less than 1% by weight, the effect of improving the impact resistance of the obtained resin composition may not be recognized, and if it is more than 40% by weight, the obtained resin composition has rigidity and heat resistance. The sex is significantly impaired.

Next, the (B) polyhydric alcohol fatty acid ester used in the present invention preferably contains at least one saturated or unsaturated fatty acid containing 10 or more carbon atoms and 2 to 6 carbon atoms. It is derived from the contained polyhydric alcohol. Polyhydric alcohols used to prepare fatty acid ester compounds include ethylene glycol,
Diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, glycerin, diglycerin, triglycerin, threitol,
One or more selected from erythritol, pentaerythritol, arabitol, ribitol, xylitol, sorbite, sorbitan, sorbitol, and mannitol. As the fatty acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, montanic acid, lignoceric acid,
Myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, 12-hydroxystearic acid, sebacic acid, dimer acid, and naturally occurring fatty acids containing such components or mixtures thereof. As the fatty acid ester compound, any of the esters of the above polyhydric alcohol and fatty acid can be used to achieve the intended purpose of the present invention, but preferably selected from palmitic acid, stearic acid, behenic acid and montanic acid. The fatty acid ester derived from the above fatty acid and a polyhydric alcohol selected from ethylene glycol, propylene glycol, glycerin, pentaerythritol, sorbitan, and sorbitol is preferable. Furthermore, it is preferably a polyhydric alcohol fatty acid ester characterized in that at least one of the hydroxyl groups of the polyhydric alcohol is not esterified. Particularly preferred fatty acid esters are exemplified by glycerin monopalmitate, glycerin monostearate, glycerin monobehenate, glycerin monomontanate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol monobehenate, pentaerythritol diester. Palmitate, pentaerythritol distearate, pentaerythritol dibehenate, pentaerythritol tripalmitate, pentaerythritol tristearate, pentaerythritol tribehenate, pentaerythritol trimontanate, sorbitan monopalmitate, sorbitan monostearate, Sorbitan monobehenate, sorbitan monomontanate, sorbitan dipalmitate, sorbitan Stearate, sorbitan dibehenate, sorbitol monostearate, sorbitol monobehenate, sorbitol monomontanate, sorbitol distearate, sorbitol dibehenate. The fatty acid ester may be used alone, or may be a mixture of two or more kinds. The amount of the fatty acid ester (B) added is 0.01 to 10% by weight, preferably 0.1 to 5% by weight, particularly preferably 0.5 to 3% by weight, based on the total composition. 0.01% by weight
If the amount is smaller, the effect of improving the fluidity is small, and it is 10% by weight.
If the amount exceeds the range, mechanical properties are adversely affected, which is not preferable.

In order to impart desired properties to the composition of the present invention according to its purpose, conventionally known additives such as antioxidants, weather resistance imparting agents, colorants, lubricants, nucleating agents, and release agents. It is possible to add one or more kinds of such as an antistatic agent, other surfactant, or an organic polymer material, an inorganic or organic fibrous, powdery, or plate-like filler.

The composition of the present invention can be prepared by the equipment and method generally known as a method for preparing a synthetic resin composition. That is, the necessary components can be mixed, kneaded using a uniaxial or biaxial extruder, extruded into pellets for molding, and then molded, and the composition can be molded by a molding machine. It is also possible to do it at the same time. Further, in order to improve the dispersion and mixing of the respective components, a method of pulverizing a part or all of the resin components, mixing and molding the pellets melt-extruded, or the like is possible. Further, the compounds such as the stabilizers and additives may be added at any arbitrary stage, and it is of course possible to add and mix them just before obtaining the final molded product. The resin composition according to the present invention can be molded by any known method such as extrusion molding, injection molding, compression molding and foam molding.

[0013]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these. The methods used to evaluate the characteristic values in the examples are as follows. 1) Impact resistance Impact resistance measurement method A pellet of the composition of Tables 1 and 2 was used to prepare a test piece of 6.4 mm thickness at a cylinder temperature of 190 ° C, and ASTM D 256
The Izod impact with notch (kg · cm / cm) was measured in accordance with. 2) Flowability Flowability (bar flow flow length) measurement method Using pellets composed of the compositions of Tables 1 and 2, a molding machine set under the following conditions was used, and thin-walled test pieces (width 5 mm x thickness) 0.3 mm) was molded, and the fluidity was evaluated from the flow length (the length filled with resin). Cylinder temperature: 190 ° C. Injection pressure: 750 kg / cm ² Injection speed: 4 m / min Mold temperature: 80 ° C. Examples 1 to 7 Polyacetal resin, (A) core shell polymer, (B) various polyhydric alcohol fatty acid ester compounds The compositions shown in Table 1 were blended, mixed using a blender, and then melt-kneaded with a 30 mm twin-screw extruder to obtain pelletized compositions. Then, the above-mentioned evaluation was performed from the pellets using an injection molding machine. The results are shown in Table 1.

Comparative Examples 1 to 7 As shown in Table 2, the polyacetal resin alone or (A)
Compositions were prepared in the same manner as in Examples 1 to 7 by adding any one component of the core-shell polymer and the polyhydric alcohol fatty acid ester compound (B) to the polyacetal resin, and the above-described evaluation was performed. The results are shown in Table 2.

The abbreviations of the components shown in the table are as follows. Polyacetal P-1 Polyplastics Co., Ltd. Duracon M90 P-2 Polyplastics Co., Ltd. Duracon M270 Core Shell Polymer A-1 Takeda Pharmaceutical Co., Ltd. Staphyloid PO-02
70 Polyhydric alcohol fatty acid ester compound B-1 Glycerin monostearate B-2 Glycerin monobehenate B-3 Pentaerythritol distearate B-4 Sorbitan dimontanate

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

As is apparent from the above description and examples, the polyacetal resin composition of the present invention obtained by adding and blending a polyhydric alcohol fatty acid ester compound to the composition of the polyacetal resin and the core-shell polymer, Improves fluidity without reducing impact resistance. Therefore, the polyacetal resin composition of the present invention is used for molded parts in all fields requiring impact resistance and fluidity, such as automobile parts (trim clips, fasteners, outer handles, fuel lids, wheel covers, front fenders, spoilers, inner handles). , Regulator handles, etc.), electrical equipment, cameras, other industrial product parts, building material piping, miscellaneous goods, household products, etc.

Claims (9)

[Claims] 1. A total of 1 to 40% by weight of (A) a core-shell polymer having a rubbery polymer core and a glassy polymer shell, and (B) 0.01 to 10% by weight of a polyhydric alcohol fatty acid ester compound. % Of a polyacetal resin composition. 2. The core-shell polymer (A) is a core-shell polymer in which substantially no anion is detected.
The polyacetal resin composition described. 3. The (A) core-shell polymer is obtained by emulsion polymerization using a nonionic surfactant and a polymerization initiator in which generated radicals are neutral.
The polyacetal resin composition described. 4. The polyacetal resin composition according to claim 1, wherein the shell of the core-shell polymer (A) is a polymer containing methyl methacrylate as a main component. 5. The polyhydric alcohol constituting the polyhydric alcohol fatty acid ester compound (B) is ethylene glycol or propylene glycol.
The polyacetal resin composition according to the item. 6. The polyhydric alcohol constituting the polyhydric alcohol fatty acid ester compound (B) is at least one selected from glycerin, pentaerythritol, sorbitan and sorbitol. The polyacetal resin composition described. 7. The (B) polyhydric alcohol fatty acid ester compound according to claim 1, wherein at least one or more hydroxyl groups of the alcohol component are not esterified and remain as hydroxyl groups. The polyacetal resin composition according to claim 1. 8. A polyacetal molding obtained by molding the composition according to claim 1. 9. The molded product according to claim 8, wherein the polyacetal molded product is an automobile clip.