JPH04339831A - Thin-wall molding of branched polyacetal resin - Google Patents

Abstract

PURPOSE:To provide a thin-wall molding of a branched polyacetal resin which object has excellent stiffness and a well-balanced combination of mechanical strength, toughness, and other properties. CONSTITUTION:The title molding is produced by molding a branched polyacetal copolymer obtained from (A) 99.8-85.0wt.% trioxane, (B) 0.1-10wt.% cyclic ether and/or cyclic formal as a comonomer, and (C) 0.1-5wt.% digylcidyl compound. It has an average wall thickness of 2mm or less and a modulus in flexure of 30,000kg/cm<2> or more as measured in accordance with ASTM D-790 (using test pieces about 0.8mm thick).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-walled molded article made of branched polyacetal resin and having high rigidity. More specifically, we will mold a polyacetal copolymer obtained by polymerizing trioxane, cyclic ethers, and glycidyl compounds, which has high rigidity in a thin molded product with a wall thickness of 2 mm or less, and has excellent fluidity and processability. This relates to a thin-walled molded product made of.

0002

[Prior Art and Problems to be Solved by the Invention] Polyacetal resin has well-balanced mechanical properties,
Due to its excellent friction and wear characteristics, chemical resistance, heat resistance, and electrical properties, it is widely used in fields such as automobiles and electrical/electronic products. Polyacetal resin has excellent chemical, thermal, and mechanical properties even without the use of special additives, but depending on the field of use, various reinforcing agents and additives may be added to further improve the above properties. Attempts have been made to improve various physical properties by incorporating improving agents. For example, inorganic fillers such as glass fiber, carbon fiber, and talc are added to polyacetal resin for the purpose of further improving rigidity. By adding these additives, the rigidity of polyacetal resin can be improved, but it can also lead to poor molding due to decreased fluidity (insufficient filling of molds for molded products), and even a small amount of addition can significantly reduce the toughness of the material. There are problems such as In particular, in the case of ultra-thin and small molded products with a wall thickness of 0.5 mm or less, the filler often becomes an obstacle and causes insufficient filling in the corners of the cavity, which is a considerable limitation in terms of application. I am receiving Furthermore, if a material containing a hard filler such as glass fiber or carbon fiber is used for the sliding part, there is a secondary problem in that the mating material is likely to wear out.

[0003] As described above, the conventionally known methods of blending reinforcing agents have various problems and are not necessarily satisfactory, and it is possible to create thin walls without sacrificing moldability or other physical properties as much as possible. A resin material that exhibits high rigidity has been desired.

0004

[Means for Solving the Problems] As a result of extensive research into the development of polyacetal resin that eliminates these drawbacks, the present inventors have discovered that a special polyacetal copolymer made by polymerizing specific monomers is an inorganic We have discovered that even without filling a filler, a thin-walled molded product has excellent rigidity, maintains excellent properties such as mechanical strength and toughness in a well-balanced manner, and has excellent fluidity and processability, and has developed the present invention. It was completed. That is, the present invention provides (A) 99.8
-85.0% by weight of trioxane, (B) 0.1 - 10% by weight of a cyclic ether and/or cyclic formal as a comonomer, and (C) 0.1 - 5% by weight of a diglycidyl compound having branches. It is made by molding a polyacetal copolymer, has an average wall thickness of 2 mm or less, and meets ASTM D-790 (test piece thickness approximately 0.8 m).
The bending elastic modulus measured by the method according to m) is 3000
The present invention provides a thin-walled branched polyacetal resin molded product exhibiting a weight of 0 kg/cm2 or more.

The branched polyacetal copolymer of the present invention will be explained in detail below. First, the main monomer constituting the polyacetal copolymer of the present invention (A
) trioxane, and (B) the comonomer are well-known materials conventionally used in the production of polyacetal copolymers. That is, trioxane is a cyclic trimer obtained from formaldehyde. In addition, (B) cyclic ether and cyclic formal as comonomers are represented by the following general formula (
2) It is a compound represented by:

[0006]

[Case 2]

Examples of such cyclic ethers and cyclic formals include epichlorohydrin, ethylene oxide,
1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3
-dioxane, propylene oxide, etc. Furthermore, cyclic esters such as β-propiolactone and vinyl compounds such as styrene or acrylonitrile are also used. Particularly preferred cyclic ethers and cyclic formals include one or more selected from ethylene oxide, dioxolane, trioxepane, and 1,4-butanediol formal. The amount of cyclic ether and cyclic formal used is 0.1 to 10% by weight, preferably 0.3 to 5% by weight, based on the total monomer mixture. If the amount is less than 0.1% by weight, the processability and thermal stability, which are characteristics of polyacetal copolymers, will be insufficient;
If it exceeds this, manufacturing itself becomes difficult.

Next, the diglycidyl compound (C) which causes the polyacetal resin to exhibit branching, which is a feature of the present invention, will be explained. The diglycidyl compound used in the production of the polyacetal copolymer of the present invention is an aliphatic ether having two glycidyl groups at its ends, and preferably a compound represented by the following general formula (3) or (4) is used.

[0009]

[Chemical formula 3]

Examples of the diglycidyl compound represented by the above formula (3) or (4) include diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, butanediol diglycidyl ether, and butanediol diglycidyl ether is particularly preferred. be. The amount of such diglycidyl compound used is 0.
1 to 5.0% by weight, preferably 0.2 to 3.0
% by weight, particularly preferably from 0.3 to 2.0% by weight. If the amount is less than 0.1% by weight, the excellent rigidity of molded products with a wall thickness of 2 mm or less, which is the objective of this application, will hardly be achieved, and if the amount is more than 5.0% by weight, excessive crosslinking reaction will occur during polymerization, resulting in production problems. This is difficult in itself, and the processability and mechanical strength of the polymer product are significantly reduced, which is not preferable.

In the present invention, the average wall thickness of the molded product is 2 m.
In view of the rigidity required for thin-walled molded products such as various motor insulators and gears, polyacetal copolymers meet ASTM D-790 (test piece thickness approximately 0.8 m).
The bending elastic modulus measured by the method according to m) is 3000
It is important that the weight is 0 kg/cm2 or more.

[0012] In addition to the above-mentioned components, the polyacetal copolymer of the present invention is polymerized using a low-molecular-weight acetal compound (D) represented by the following general formula (1) in order to adjust its molecular weight.

[0013]

[C4]

This can be carried out in the presence of Formula (1)
Examples of the low molecular weight acetal compound (D) include methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, oxymethylene di-
Examples include n-butyl ether, and methylal is preferred. The amount of the substance (D) added is adjusted between 0 and 1000 ppm depending on the required molecular weight (melt viscosity) of the branched copolymer.

The method for polymerizing such a polyacetal copolymer may be carried out in accordance with the well-known method for polymerizing a trioxane copolymer. That is, a cationically active catalyst is generally used as the catalyst. Examples of such catalysts include Lewis acids, especially halides such as boron, tin, titanium, phosphorous, arsenic and antimony, such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorous pentachloride, pentachloride, etc. Compounds such as phosphorus fluoride, arsenic pentafluoride and antimony pentafluoride, and their complexes or salts, protic acids such as trifluoromethanesulfonic acid, perchloroic acid, esters of protic acids, especially perchloric acid and lower aliphatic alcohols. Esther with (
(e.g. perchloric acid tertiary butyl ester), anhydrides of protonic acids, especially mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids (e.g. acetyl perchlorate), or isopoly acids, heteropolyacids (e.g. phosphomolybdic acid) , or triethyloxonium hexafluorophosphate, triphenylmethylhexafluoroarzenate, acetylhexafluoroborate, and the like. Among these, boron fluoride or a coordination compound of boron fluoride and an organic compound (eg, ether) is the most common and suitable.

[0016] The polymerization reaction can be carried out either batchwise or continuously, or by solution polymerization or melt bulk polymerization, but liquid monomers are used and as the polymerization progresses, a solid powdery block of polymer is formed. This is a common method. In this case, an inert liquid medium can also be present if necessary. As the polymerization equipment, a generally used reaction tank with a stirrer can be used for batch type, and for continuous type, co-kneader, twin screw type continuous extrusion mixer, twin screw paddle type continuous mixer, etc. Continuous polymerization devices for trioxane and the like that have been proposed so far can be used. The polymerization temperature ranges from 64 to 120°C. Within this range, relatively low temperatures are more desirable. In addition, the polymerization time is related to the amount of catalyst, and there is no particular restriction, but it is generally 0.
．． A polymerization time of 5 to 100 minutes is chosen. The polymer taken out from the exit of the polymerization machine after a predetermined period of time is usually in the form of lumps or powder, and some or all of the unreacted monomers are separated and post-processes such as stabilization are performed using conventional methods to improve stability. A high copolymer can be obtained.

190 of branched polyacetal copolymer resin
℃, 2.16Kg standard load (ASTM D-1238-
57T) is in the range of 0.01 to 60 (g/10 min), and from the viewpoint of practical mechanical properties, moldability, etc., it is preferably in the range of 0.5 to 30. preferable. Such branched polyacetal copolymer resins generally have a high dependence of viscosity on shear rate, and are characterized by good moldability considering their high molecular weight. Additionally, the branched polyacetal resin copolymer obtained in this way surprisingly has high rigidity in thin walls that cannot be obtained with linear copolymers, and can be used without adding any known inorganic fillers. Even when used as is, it exhibits the rigidity generally required for thin-walled gears, springs, etc., and has improved mechanical strength, without the drawbacks of conventional resins containing inorganic fillers, etc., and is suitable as a thin-walled, highly rigid material. It is a feature of the present invention that it has not been previously known that branched polyacetal copolymers exhibit such properties.

The polyacetal copolymer of the present invention can be mixed with a linear polyacetal homopolymer or a polyacetal copolymer whose main chain is mostly composed of oxymethylene chains, as long as the purpose is not impaired. Furthermore, in order to impart physical properties to the polyacetal copolymer of the present invention depending on the intended use, various known additives, such as various stabilizers, colorants, lubricants, mold release agents, nucleating agents, and charging agents, are added to the polyacetal copolymer of the present invention. inhibitors, other surfactants, different polymers, organic modifiers, inorganic or organic fibrous, powdery, plate-like fillers, etc. (e.g. glass fibers, glass flakes, glass powder,
Of course, it is also possible to incorporate other substances (glass beads, talc, mica, etc.).

[0019] Specific examples of thin-walled molded products made from such a polyacetal copolymer include insulators for various motors, precision parts such as watch gears, fans,
Examples include computer keyboard frames and floppy disk components, but the thinner the molded product is, the more preferable it is, and it is particularly suitable as a thin-walled molded product with an average wall thickness of 1 mm or less.

[0020]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

Examples 1 to 5 A barrel with a jacket, which has a cross section in which two circles with an inner diameter of 80 mm partially overlap each other, has an effective length of 1.3 m, and allows the heat medium to pass through the outside, and inside the barrel there are a number of barrels that mesh with each other. Using a continuous mixing reactor consisting of two rotating shafts with paddles, hot water at 80°C was passed through the jacket, and the two rotating shafts were rotated in different directions at a speed of 100 rpm. A trioxane mixture having the composition shown is continuously fed at a rate of 10 kg/hour, and at the same time, a predetermined amount of a cyclohexane solution of boron trifluoride dibutyl etherate is continuously added to the same place to carry out copolymerization. The reaction mixture discharged from the reactor was immediately poured into water containing 0.1% triethylamine to deactivate the polymerization catalyst. Next, the polymer was washed with acetone and air-dried for stabilization to obtain a branched polyacetal copolymer.

Comparative Examples 1 to 3 (C) Using a small amount or not using a diglycidyl compound, (A) trioxane and (B) shown in Table 1
Polymerization was carried out using a cyclic ether in the same manner as in the examples, and a substantially linear polyacetal polymer was obtained through a stabilization step.

The polyacetal (co)polymers obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were molded into test pieces, and the thin flexural modulus and tensile strength were measured. The results are summarized in Table 1. In addition, the test method and measurement method are as follows. 1) Thin-wall bending characteristics: Using test pieces with thicknesses of 0.8 mm and 1.6 mm,
The flexural modulus and flexural strength were measured using a measurement method based on ASTM D-790. 2) Method for measuring fluidity (bar flow flow length) Using pellets made of the composition in Table 1, a thin test piece (width 5 mm x thickness 0.5 mm) was prepared using a molding machine set to the following conditions.
was molded, and its fluidity was evaluated from its flow length (length filled with resin). Cylinder temperature 190℃ Injection pressure 500 kg/cm2 Mold temperature 80℃

[0024]

[Table 1]

[0025]

Effects of the Invention As is clear from the above description and examples, the branched polyacetal resin obtained by polymerizing trioxane, cyclic ether and/or cyclic formal, and diglycidyl compound has It has excellent mechanical properties in thin-walled molded products, especially high rigidity expressed by flexural modulus without significantly reducing toughness, and is extremely preferred as a material for small-sized and thin molded products. For this reason, it is used in automobiles, electric/electronic parts, etc. that require small size and high output, such as motor-related parts such as insulators, gears, and fans, computer keyboard frames, floppy disk components, and thin-walled spring characteristics. Suitable for lock-related parts such as snap-fits.

Claims (6)

[Claims] Claim 1: (A) 99.8 to 85.0% by weight trioxane; (B) 0.1 to 10% as a comonomer;
It is formed by molding a polyacetal copolymer having branches consisting of cyclic ether and/or cyclic formal in an amount of 0.1 to 5% by weight of (C) a diglycidyl compound, and has an average wall thickness of 2 mm or less, and ASTM D-
A thin-walled branched polyacetal resin molded product exhibiting a flexural modulus of 30,000 kg/cm2 or more as measured by a method similar to 790 (test piece thickness: approximately 0.8 mm). 2. The thin-walled branched polyacetal resin molded article according to claim 1, wherein component (B) is one or more selected from ethylene oxide, dioxolane, trioxepane, and 1,4-butanediol formal. 3. The thin-walled branched polyacetal resin molded article according to claim 1 or 2, wherein the diglycidyl compound (C) is an alkylene oxide diglycidyl ether. [Claim 4] The polyacetal copolymer is (D)
The thin-walled branched polyacetal resin molded article according to any one of claims 1 to 3, which is polymerized in the presence of a low molecular weight acetal compound represented by the following general formula (1). [Chemical formula 1] 5. The thin-walled molded article according to claim 1, which is made of a branched polyacetal resin and has an average wall thickness of 1 mm or less. 6. The thin-walled branched polyacetal resin molded product according to claim 1, which is used as an insulator for various motors, a precision part such as a watch gear, a fan, a computer keyboard frame, or a component for a floppy disk.