JPH04146949A - Polyacetal resin composition - Google Patents

Abstract

PURPOSE:To prevent delamination and improve heat resistance, rigidity, bending strength, and impact strength by compounding a polyacetal resin with an ethylene-ethyl acrylate copolymer modified with an organopolysiloxane. CONSTITUTION:100 pts.wt. ethylene-ethyl acrylate copolymer contg. 10-50wt.% ethyl acrylate, 10-800 pts.wt. organopolysiloxane of the formula [wherein R<1> is an unsatd. aliph. group; R<2> is an optionally substd. monovalent hydrocarbon group contg. no unsatd. aliph. group; 0<=a<1; 0.5<b<3; and 1<a+b<3] having a viscosity at 23 deg.C of 10cSt or higher, and 0.01-1 pt.wt. org. peroxide having a 10-min half-life temp. of 100-220 deg.C (e.g. t-butylperoxy isopropyl carbonate) are thermally mixed at 160-200 deg.C to give an ethylene-ethyl acrylate copolymer modified with the organopolysiloxane. 100 pts.wt. polyacetal resin having a melt flow rate of 0.1-50g/10min and contg. 80mol% or higher oxymethylene units is compounded with 1-30 pts.wt. the modified ethylene-ethyl acrylate copolymer.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a polyacetal resin composition that has excellent heat resistance, rigidity, bending strength, impact resistance, etc., has no drawbacks such as delamination, and has excellent moldability.

[Conventional technology]

Polyacetal resin has excellent heat resistance, mechanical properties,
It has creep properties, lubricating properties, and electrical properties, and is widely used in automobile parts, electronic/electrical equipment parts, audio equipment parts, water supply equipment parts, toy parts, etc. Furthermore, the mechanical properties of polyacetal resins have little temperature dependence and can be used under a wide range of temperature conditions. However, this resin has drawbacks such as low notched impact strength (and is prone to breakage if there are residual stress or minute scratches during molding), and is used for molding mechanical parts such as gears, bolts, nuts, etc., and molding of complex shapes. It is unsuitable for molding products, and it is necessary to improve its impact resistance. Conventionally, methods for improving the impact resistance of polyacetal resin include adding an ionomer to polyacetal resin (as described in 45-18023) and the addition of ethylene-ethyl acrylate copolymer (Japanese Patent Publication No. 45-2623).However, molded products made from such resin compositions cause delamination, The problem remains that mechanical strength, especially notched isot impact strength, is low.

[Problem to be solved by the invention]

In view of these circumstances, the present invention aims to provide a polyacetal resin composition that prevents mechanical parts such as gears, bolts, and nuts manufactured from polyacetal resin from being easily damaged by impact, and that has particularly excellent notched isot impact strength. Take it as a challenge.

[Means to solve the problem]

As a result of extensive research, the present inventors have found that the above-mentioned problem of notched isot impact strength can be improved by blending a specific amount of organopolysiloxane-modified ethylene-ethyl acrylate copolymer into polyacetal resin. Heading: The invention has been completed. That is, the present invention relates to a polyacetal resin composition characterized in that 1 to 30 parts by weight of an organopolysiloxane-modified ethylene-ethyl acrylate copolymer is blended with 100 parts by weight of a polyacetal resin. Next, the present invention will be explained in more detail. The organopolysiloxane-modified ethylene ethyl acrylate copolymer is an ethylene-ethyl acrylate copolymer (hereinafter referred to as EEA) having an ethyl acrylate (hereinafter referred to as EA) content of 10 to 50%.
With respect to 100 parts by weight, (A) the following formula l2 R'a R2b S+ 0□ (I) (wherein, R1 is an aliphatic unsaturated group, and R2 is an unsubstituted or substituted 1 that does not contain an aliphatic unsaturated group) represents a valent hydrocarbon group, a
and b satisfy the following conditions: 0≦a<1.0.5<b<
3, 10 to 800 parts by weight of an organopolysiloxane represented by (representing a numerical value satisfying l<B+b<3), and (
B) An organopolysiloxane-modified ethylene-ethyl acrylate copolymer (hereinafter referred to as an EEA-modified product) obtained by heating and kneading a composition containing 0.01 to 1 part by weight of an organic peroxide is preferred. The EEA used in the production of the EEA modified product of the present invention has an EA content of 10 to 50%. This is because when the EA content is less than 10%, the notched Izot impact strength is not significantly improved when the resulting EEA modified product is added to the polyacetal resin, whereas EEA with an EA content of more than 50% causes its own stickiness and blocking. is terrible,
This is because crosstalk is difficult and impractical. In addition, EEA
As such, ordinary commercially available products can be used. The organopolysiloxane used in the present invention is represented by the above formula I, in which the R' group is a vinyl group,
Examples include allyl group, acrylic group, methacryl group, etc.
2 is an alkyl group such as a methyl group, an ethyl group, a propyl group, an aryl group such as a phenyl group or a tolyl group, a cycloalkyl group such as a cyclohexyl group or a cyclobutyl group, or a hydrogen atom bonded to a carbon atom of these hydrocarbon groups. Examples include groups partially substituted with halogen atoms, cyano groups, mercapto groups, etc., but these may be the same or different combinations. Further, in the above formula I, a is 0 or greater than O and less than 1. This range is due to the fact that when a is 1 or more, the molded product produced by the present invention becomes too hard. a is preferably 0.0004 to 0.06. In the above formula I, b is greater than 0.5 and less than 3. If this range is 0.5 or less, it is difficult for the composition of the present invention to cross paths, resulting in poor processability, and if it is 3 or more, the molded product produced by the present invention becomes too hard, which is undesirable. b is preferably 1-2. The molecular structure of the organopolysiloxane in the present invention is:
If it is expressed by the above formula ■, it is linear, branched,
It may be circular, reticular, three-dimensional reticular, or the like. Such organopolysiloxanes include, for example, those commercially available as tear strength improvers for silicone rubber.
One may mention so-called silicone gum stocks. In addition, the linear organopolysiloxane used in the present invention has the general formula % (wherein R represents an unsubstituted or substituted monovalent hydrocarbon group,
(n represents a number of 10 or more) and is generally called silicone oil. R in the above formula is a group selected from an alkyl group, an aryl group, and a hydrogen atom, and is a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, and a t-butyl group. Typical examples include phenyl group, phenyl group, and hydrogen atom. All R's in the molecule may be the same, or some of the R's may be different groups, or some of the R's may be a vinyl group or a hydroxyl group. n is 10 or more, and preferably 100 to 1000. If n is less than 10, it will be difficult to knead with polyethylene. The viscosity at 23°C of the organopolysiloxane polymer represented by the above formula 1 used in the present invention is loC
S or higher, preferably 10" to io@cs. If the viscosity is lower than 10C3, heating and kneading is difficult, and the organopolysiloxane polymer may ooze out from the surface of the molded product. Can be used in the present invention. The organic peroxide preferably has a decomposition temperature of 100 to 220°C with a half-life of 10 minutes, that is, one with a 10-minute half-life temperature (Tp) of 100 to 220°C. Examples of such organic peroxides include the following: [However, the value in parentheses is the decomposition temperature (°C)] t-Butylperoxyisopropyl carbonate (13
5), t-butylberoxylaure) (1,40)
, 2,5-dimethyl-2,5 di(benzoylperoxy)hexane (140), t-butylperoxyacetate (140), di-t-butyldiperoxyphthalate (140), +-butylperoxymaleic acid (140)
), cyclohexanone peroxide (145), t-
Butylperoxybenzony-1-(145), dicumylperoxide (150), 2,5-dimethyl-2,5-
Di(t-butylperoxy)hexane (155), t-
butyl cumyl peroxide (155), t-butyl hydroperoxide (158), di-t-butyl peroxide (160), 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 ( 170), -isopropylbenzene hydroperoxide (170), p-menthane hydroperoxide (180), 2,5-dimethylhexane-2,5-dihydroperoxide (2+ 3
). In the present invention, the amount of organopolysiloxane is EE
The amount is 10 to 800 parts by weight based on 00 parts by weight of Al. This is because if the amount is less than 10 parts by weight, the effect of improving the impact resistance of the polyacetal resin is difficult to be observed, and if it exceeds 800 parts by weight, the solubility in the polyacetal resin deteriorates. In the present invention, the amount of organic peroxide is 0.01 to 1 part by weight per 100 parts by weight of EEA. This is 0.0
If the amount is less than 1 part by weight, the modification reaction is difficult to occur (on the other hand, if it exceeds 1 part by weight, the reaction effect is hardly improved. Also, if the amount added is too large, gels will increase in the EEA modified product). It is not preferable.A commonly used crosslinking aid can also be used in combination with an organic peroxide.In the present invention, it is preferable to carry out cross-crossing at a temperature of 160 to 200°C. In the present invention, the EEA modified product as described above is used together with the following polyacetal resin.The polyacetal resin used in the present invention has oxy-oxygen in its main chain. It usually contains 80 mol% or more of methylene units, and has a melt flow rate (VFR) (190°C) of 0.1 to 50 as measured by ASTM D1288.
g/10 minutes is desirable. The homopolymer is produced, for example, by introducing substantially anhydrous formaldehyde into an organic solvent containing a basic polymerization catalyst such as an organic amine, polymerizing it, and then acetylating the ends with acetic anhydride. Alternatively, the copolymer can be prepared by dissolving or suspending substantially anhydrous trioxane and copolymer components such as ethylene oxide or 1,3-dioxolane in an organic solvent such as cyclohexane, and then dissolving or suspending the copolymer with boron trifluoride diethyl ether. It is produced by polymerizing by adding a Lewis acid catalyst such as Lato, and decomposing and removing unstable terminals with a basic compound. Alternatively, it can be produced by introducing hetrioxane, a copolymerization component, and a catalyst into a self-cleaning stirrer without using any solvent, performing bulk polymerization, and then adding a basic substance to decompose and remove unstable terminals. You can. In the present invention, the amount of the EEA modified compound is 1 to 30 parts by weight per 100 parts by weight of the polyacetal resin. If it is less than 1 part by weight, the effect of improving impact resistance is low;
If it exceeds 0 parts by weight, heat resistance and rigidity will decrease. In addition, in the present invention, polyacetal resin and EEA
Mixing with modified substances can be performed using known methods. For example, a single screw extruder, a twin screw extruder, a roll, a Banbury mixer, a kneader-Henschel mixer, etc. can be used. The obtained polyacetal resin composition is molded by known methods such as injection molding, extrusion molding, foam molding, rotational molding, compression molding, etc., and is used for automotive parts, electronic and electrical equipment parts, piping parts, and building materials. It is molded into industrial parts, miscellaneous goods-related materials, precision machine parts, etc. The composition of the present invention is particularly suitable for mechanical parts such as gears, bolts, nuts, etc., and molded products of complex shapes that require excellent notched impact strength. Conventional resin additives may be added to the compositions of the present invention. For example, antioxidants, lubricants, various organic or inorganic pigments, ultraviolet inhibitors, dispersants, neutralizing agents, nucleating agents, crosslinking agents, flow improvers, dyes, carbon black, flame retardants, asbestos, glass fibers, Titanic acid whiskers, talc, silica, calcium carbonate, pumice, silica alumina, kaolin, mica, etc. may be added to the extent that they do not impair the physical properties of the molded article produced from the polyacetal resin composition of the present invention.

【Example】

Next, the present invention will be explained in more detail based on Examples, but the present invention is not limited thereto. Example I 100 parts by weight of EEA (manufactured by Nippon Unicar, trade name NUC-6570) with an EA content of 25%, 70 parts by weight of a silicone gum stock with a viscosity of 300,000 C3 at 23°C and a methylvinyl silicone content of 1.0%, an organic Peroxide (manufactured by NOF Corporation, trade name Perhexine 25B)
0.1 part by weight, and antioxidant (manufactured by Civer Geigy,
0.02 parts by weight of Irganox 1010 (trade name) was kneaded at 180° C. for 15 minutes using a Banbury mixer, and the kneaded product was extruded using an extruder to obtain a pelletized resin composition. The melt index (MI) of this pellet is J
Measured according to IS-6760. In addition, the pellets were molded using a hot press molding machine at 180°C and 100kg/
An? A sheet was manufactured by pressing the sheet, and the tensile strength and elongation of the sheet were also measured in accordance with JIIK6760. Examples 2 and 3 The same procedure as Example 1 was repeated except that the amount of silicone gum stock was varied as shown in Table 1. Comparative Examples 1 to 3 The same operations as in Examples 1 to 3 were repeated except that EEA was changed to one with an EA content of 7% (manufactured by Nippon Unicar, trade name NU (-6220)). The above Examples 1 to 3 The production conditions and evaluation results of the EEA-modified products produced in Comparative Example 1-3 are summarized in Table 1.Next, tests were conducted on polyacetal-based resin compositions in which these EEA-modified products were blended with polyacetal-based resin. An example is shown. Example 4 5 parts by weight of the EEA modified pellets obtained in Example 1 were added to 100 parts by weight of a polyacetal resin (manufactured by DuPont Japan, trade name: Delrin 100) with an MFR of 2.3 g/10 minutes. was added and mixed for 20 minutes in a Henschel mixer.The mixture was transferred to a 40 m
It was extruded using a screw extruder and pelletized. Thereafter, injection molding was carried out at a cylinder temperature of 230°C, an injection pressure of 1 ton/cnf, and a mold temperature of 90°C.
-256 notched) was measured. Examples 5 to 7 The same operation as in Example 4 was repeated except that the amount of EEA modified pellets added was changed. Examples 8 and 9 The same operation as in Example 4 was repeated except that the EEA modified products obtained in Examples 2 and 3 were used, respectively. Comparative Examples 4 to 6 The same operations as in Example 4 were repeated except that the EEA modified products obtained in Comparative Examples 1 to 3 were used, respectively. Comparative Examples 7 to 9 The same operations as in Example 4 were repeated except that unmodified EEA (NUC-6570 shown in Example 1) was used instead of the modified EEA. Comparative Example 1O The same measurements as above were carried out using only Delrin 100, a polyacetal resin. The test conditions and results of Examples 4 to 9 and Comparative Examples 4 to 10 are summarized in Table 2. Table 2: The bid was accepted with 11 copies of the counterfeit name.

【Effect of the invention】

As explained in detail above, the polyacetal resin composition of the present invention has an organopolysiloxane-modified ethylene-
Since ethyl acrylate copolymer is added, in addition to the excellent heat resistance, mechanical properties, creep properties, lubrication properties, and electrical properties that polyacetal resins inherently have,
Notched Izot impact strength is greatly increased. Therefore, the composition of the present invention can be widely applied to fields requiring impact resistance, particularly mechanical parts such as gears, bolts, and nuts, and molded products with complex shapes. Patent applicant Nippon Unicar Co., Ltd.

Claims (2)

[Claims] (1) A polyacetal resin composition characterized in that 1 to 30 parts by weight of an organopolysiloxane-modified ethylene-ethyl acrylate copolymer is blended with 100 parts by weight of a polyacetal resin. (2) The organopolysiloxane-modified ethylene-ethyl acrylate copolymer has an ethyl acrylate content of 10
~50% ethylene-ethyl acrylate copolymer 1
For 00 parts by weight, (A) the following formula I: R^1_aR^2_bSiO(_4_-_a_-_b/
2) (I) (In the formula, R^1 is an aliphatic unsaturated group, R^2
represents an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated group, and a and b satisfy the following conditions: 0≦a<1, 0.5<b<3, 1<a+b<3 Organopolysiloxane represented by 10~
800 parts by weight of the polyacetal resin composition according to claim 1, which is an organopolysiloxane-modified ethylene-ethyl acrylate copolymer obtained by heating and kneading a composition containing 0.01 to 1 part by weight of (B) an organic peroxide. thing.