Polyacetal copolymer and method for producing the same

Abstract

To provide a novel polyacetal copolymer excellent in productivity and mechanical characteristics by introducing a group having a new structure and to provide a method for producing the polyacetal copolymer.SOLUTION: There are provided: a polyacetal copolymer produced by subjecting at least (A) trioxane, (B) a cyclic acetal compound having a 2C or more oxyalkylene group in the ring and (C) organopolysiloxane to polymerization reaction in which the organopolysiloxane (C) is a condensate of one or more kinds of silane compounds selected from compounds represented by the following formula (1): R1nSi(OR2)4-n (1) and is a compound having an alkoxy group, provided that in formula (1), R1 represents a monovalent hydrocarbon group and R2 represents a 4C or less alkyl group; and n is an integer of 0 to 3; and a method for producing the polyacetal copolymer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a novel polyacetal copolymer excellent in productivity and mechanical properties and a method for producing the same.

Background Art

[0002] Polyacetal resins have excellent properties in terms of mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., and are mainly used as structural materials and mechanical parts in electrical equipment, automotive parts, precision mechanical parts, etc. However, as the fields in which polyacetal resins are used expand, the required properties tend to become increasingly advanced, complex, and specialized. As such required properties, while maintaining the excellent slidability, appearance, etc. inherent in polyacetal resins, further improvement in mechanical strength is required.

[0003] On the other hand, for the purpose of simply improving rigidity, a method of filling a polyacetal resin with a fibrous filler or the like is common, but this method has problems such as poor appearance of molded products due to filling with a fibrous filler or the like, deterioration of sliding characteristics, and further deterioration of toughness.

[0004] In addition, in polyacetal copolymers, it is known that by reducing the amount of comonomer, the rigidity can be improved without substantially impairing the slidability and appearance. However, in the method of reducing the amount of comonomer, problems such as not only a decrease in toughness but also a decrease in the thermal stability of the polymer occur, and it has not necessarily been able to meet the requirements.

[0005] Attempts have also been made to improve rigidity by introducing a branched structure. However, depending on the type of comonomer, when a cationic polymerization catalyst, particularly a protonic acid, is used as the polymerization catalyst, the polymerization initiation may be delayed and polymerization may occur suddenly and explosively, and there are also problems from the viewpoint of production stability.

[0006] For example, regarding polyacetal copolymers, a copolymer obtained by copolymerizing trioxane and a compound having two or more glycidyl ether groups in one molecule has been proposed (Patent Document 1). However, when using a compound having a plurality of epoxy groups typified by glycidyl ether groups and ether oxygen as functional groups for polymerization, there are still problems with polymerization stability. In particular, when a protonic acid is used as a polymerization catalyst, polymerization does not occur at a low catalyst amount, and when the catalyst amount is increased, a phenomenon occurs in which a sudden violent polymerization reaction occurs after an irregular induction period, making it difficult to control the polymerization.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a method for producing a novel polyacetal copolymer excellent in productivity and mechanical properties.

Means for Solving the Problems

[0009] The object of the present invention has been achieved as follows. 1. A polyacetal copolymer obtained by subjecting at least trioxane (A), a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and an organopolysiloxane (C) to a polymerization reaction, wherein the organopolysiloxane (C) is a condensate of one or more silane compounds selected from the compounds represented by the following formula (1) and is a compound having an alkoxy group. R 1 n Si(OR 2 ) 4-n (1) In formula (1), R 1 represents a monovalent hydrocarbon group, and R 2represents an alkyl group having 4 or fewer carbon atoms. n is an integer from 0 to 3. 2. R in the formula (1) 2 The polyacetal copolymer according to 1, wherein is at least one selected from a methyl group and an ethyl group. 3. R in the formula (1) 1 The polyacetal copolymer according to 1 or 2, wherein is at least one selected from a methyl group and a phenyl group. 4. A method for producing a polyacetal copolymer by polymerizing at least trioxane (A), a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and an organopolysiloxane (C) in the presence of a cationic polymerization catalyst, wherein the organopolysiloxane (C) is a condensate of one or more silane compounds selected from the compounds represented by the following formula (1) and is a compound having an alkoxy group. A method for producing a polyacetal copolymer. R 1 n Si(OR 2 ) 4-n (1) In the formula (1), R 1 represents a monovalent hydrocarbon group, and R 2 represents an alkyl group having 4 or fewer carbon atoms. n is an integer from 0 to 3. [Effect of the Invention]

[0010] According to the present invention, it is possible to provide a novel polyacetal copolymer excellent in productivity and mechanical properties and a method for producing the polyacetal copolymer. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be appropriately modified and implemented within the scope of the object of the present invention.

[0012] [Polyacetal Copolymer] The polyacetal copolymer of the present invention is a condensate of trioxane (A), a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and one or more specific silane compounds, and is a copolymer obtained by subjecting an organopolysiloxane (C) having an alkoxy group to a polymerization reaction.

[0013] Since the polyacetal copolymer of the present invention has a structure in which the terminals of a plurality of polyacetal molecules are bonded to an organopolysiloxane, it is considered to have excellent mechanical properties.

[0014] ≪Trioxane (A)≫ The trioxane (A) used in the present invention is a cyclic trimer of formaldehyde, and is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and is purified by a method such as distillation and then used.

[0015] ≪Cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring≫ In the present invention, it is possible to use a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring as a comonomer.

[0016] The cyclic acetal compound having an oxyalkylene group having 2 or more carbon atoms in the ring of the present invention is a compound generally used as a comonomer in the production of a polyacetal copolymer, and specifically includes 1,3-dioxolane, 1,3,6-trioxocane, 1,4-butanediol formal, and the like.

[0017] In the present invention, the component (B) is preferably used in the range of 0.01 to 20 parts by mass, more preferably in the range of 0.05 to 5 parts by mass, based on 100 parts by mass of trioxane.

[0018] ≪Organopolysiloxane (C) having an alkoxy group, obtained by condensing one or more silane compounds selected from the silane compounds represented by formula (1)≫ R 1 n Si(OR 2 ) 4-n (1) In formula (1), R 1 represents a monovalent hydrocarbon group, and R 2 represents an alkyl group having 4 or fewer carbon atoms. n is an integer from 0 to 3.

[0019] Examples of the silane compound represented by formula (1) include phenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methylphenyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, and the like.

[0020] The organopolysiloxane (C) of the present invention is obtained by condensing one or more silane compounds selected from the silane compounds represented by formula (1) using a known condensation reaction catalyst, specifically, an acid catalyst, a base catalyst, an organometallic compound catalyst, or the like.

[0021] Specifically, for example, the (alkoxy)silane compound is subjected to partial hydrolysis and condensation by the method described in Japanese Patent Publication No. 2904317, Japanese Patent Publication No. 3389338, or the like, and contains an alkoxy group to such an extent that the effects of the present invention are achieved.

[0022] The fact that the organopolysiloxane (C) of the present invention has an alkoxy group can be known by quantifying the alkoxy group in the organopolysiloxane. For example, 29 it can be quantified by Si-NMR measurement or the amount of alcohol produced when decomposed by heating after adding KOH.

[0023] The organopolysiloxane (C) of the present invention is a compound containing an alkoxy group and optionally a hydrocarbon group and having a siloxane skeleton. Specific examples of the alkoxy group include, for example, a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

[0024] Specific examples of the hydrocarbon group include saturated hydrocarbon groups such as a methyl group, an ethyl group, and a propyl group, and aromatic hydrocarbon groups such as a phenyl group and a naphthyl group. R in the formula (1) related to the organopolysiloxane (C) of the present invention 2 is preferably at least one selected from a methyl group and an ethyl group from the viewpoint of the mechanical properties of the resulting polyacetal copolymer.

[0025] Also, R in the formula (1) related to the organopolysiloxane (C) 1 is preferably at least one selected from a methyl group or a phenyl group from the viewpoint of the mechanical properties of the resulting polyacetal copolymer.

[0026] Commercially available products of the organopolysiloxane (C) of the present invention include, for example, "SR2402Resin", "AY42-163", "DC-3074intermediate", and "DC-3037intermediate" (manufactured by Dow Corning Toray Co., Ltd.), "KC-89S", "KR-500", "X-40-9225", "X-40-9246", "X-40-9250", "KR-9218", "KR-213", "KR-510", "X-40-9227", "X-40-9247", "KR-401N" (manufactured by Shin-Etsu Chemical Co., Ltd.), and the like.

[0027] In the present invention, the component (C) is considered to function as a chain transfer agent in the polymerization reaction. As a result, when performing the polymerization reaction of trioxane (A), the cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and the organosiloxane (C), the control of the polymerization becomes easy, and the productivity is considered to be improved.

[0028] In the present invention, the component (C) is preferably used in an amount in the range of 0.01 to 5 parts by mass, more preferably 0.03 to 1 part by mass, based on 100 parts by mass of the trioxane (A).

[0029] <Cationic polymerization catalyst> As the cationic polymerization catalyst, a polymerization catalyst known in cationic copolymerization using trioxane (A) as the main monomer can be used. Typically, a protonic acid and a Lewis acid can be mentioned. In particular, a protonic acid is preferable.

[0030] ≪Protonic acid≫ Examples of the protonic acid include perfluoroalkane sulfonic acid, heteropoly acid, isopoly acid and the like. Specific examples of the perfluoroalkane sulfonic acid include trifluoromethane sulfonic acid, pentafluoroethane sulfonic acid, heptafluoropropane sulfonic acid, nonafluorobutane sulfonic acid, undecafluoropentane sulfonic acid, tridecafluorohexane sulfonic acid, pentadecafluoroheptane sulfonic acid, heptadecafluorooctane sulfonic acid.

[0031] The heteropoly acid refers to a polyacid formed by dehydration condensation of different oxyacids, having a specific different element at the center, and having a mononuclear or polynuclear complex ion formed by sharing oxygen atoms and condensing condensed acid groups. The isopoly acid, also referred to as an isopolyacid, a homonuclear condensed acid, or a homopolyacid, refers to a high molecular weight inorganic oxyacid composed of a condensate of an inorganic oxyacid having a single type of metal with a valence of V or VI.

[0032] Specific examples of the heteropoly acid include phosphomolybdic acid, phosphotungstic acid, phosphomolybdotungstic acid, phosphomolybdovanadic acid, phosphomolybdotungstovanadic acid, phosphotungstovanadic acid, silicotungstic acid, silicomolybdic acid, silicomolybdotungstic acid, silicomolybdotungstovanadic acid and the like. In particular, from the viewpoint of polymerization activity, the heteropoly acid is preferably selected from silicomolybdic acid, silicotungstic acid, phosphomolybdic acid, and phosphotungstic acid.

[0033] Specific examples of the isopolyacid include isopolytungstic acid exemplified by paratungstic acid, metatungstic acid, etc., isopolymolybdic acid exemplified by paramolybdic acid, metamolybdic acid, etc., metavanadic acid, isopolyvanadic acid, etc. Among them, from the viewpoint of polymerization activity, isopolytungstic acid is preferable.

[0034] ≪Lewis acid≫ Examples of the Lewis acid include halides of boron, tin, titanium, phosphorus, arsenic, and antimony. Specifically, boron trifluoride (and its ether complex), tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and their complex compounds or salts can be mentioned.

[0035] The amount of the polymerization catalyst is not particularly limited, but it is preferably 0.1 ppm or more and 50 ppm or less, more preferably 0.1 ppm or more and 30 ppm or less, based on the total of all monomers.

[0036] In the present invention, in addition to the above components, a component for adjusting the molecular weight can be used in combination to adjust the amount of end groups. Examples of the component for adjusting the molecular weight include a chain transfer agent that does not form an unstable end group, that is, a compound having an alkoxy group such as methylal, monomethoxymethylal, dimethoxymethylal, etc.

[0037] The polymerization apparatus used in the present invention is not particularly limited, and a known apparatus can be used, and any method such as a batch method or a continuous method is possible. Further, the polymerization temperature is preferably maintained at 65°C or higher and 135°C or lower.

[0038] The cationic polymerization catalyst is preferably diluted with an inert solvent that has no adverse effect on the polymerization and used.

[0039] The deactivation of the polymerization catalyst after polymerization can be carried out by a conventionally known method. For example, after the polymerization reaction, a basic compound or its aqueous solution can be added to the resulting reaction product discharged from the polymerization machine or the reaction product in the polymerization machine.

[0040] The basic compound for neutralizing and deactivating the polymerization catalyst is not particularly limited. After polymerization and deactivation, if necessary, washing, separation and recovery of unreacted monomers, drying, etc. are carried out by conventionally known methods.

[0041] The polyacetal copolymer obtained as described above preferably has a weight average molecular weight equivalent to polymethyl methacrylate determined by size exclusion chromatography of 10,000 to 500,000, particularly preferably 20,000 to 150,000. Also, regarding the end groups, 1 the amount of hemiacetal end groups detected by 1H-NMR (for example, by the method described in JP-A-2001-11143) is preferably 0 to 4 mmol / kg, particularly preferably 0 to 2 mmol / kg.

[0042] In order to control the amount of hemiacetal end groups within the above range, it is preferable that the impurities, particularly water, in the total amount of the monomers and comonomers used for polymerization be 20 ppm or less, particularly preferably 10 ppm or less. <Other components>

[0043] It is preferable to blend various known stabilizers selectively used as needed in the polyacetal copolymer produced by the present invention. Examples of the stabilizer used here include any one or two or more of hindered phenol compounds, nitrogen-containing compounds, hydroxides of alkali or alkaline earth metals, inorganic salts, carboxylates, etc.

[0044] Furthermore, to the polyacetal copolymer produced by the present invention, if necessary, general additives for thermoplastic resins, such as colorants such as dyes and pigments, lubricants, nucleating agents, mold release agents, antistatic agents, surfactants, or one or more of organic polymer materials, inorganic or organic fibrous, powdery, plate-like fillers, etc. can be added.

Examples

[0045] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[0046] <Polymerization reaction> 300 g of trioxane (A) was placed in a sealed autoclave having a jacket through which a heat medium can pass and stirring blades, and further, the compound described in Table 1 as the component (C) and 1,3-dioxolane (DO) as the component (B) were added so as to have the mass ratio shown in Table 1, respectively. These contents were stirred, and after maintaining the internal temperature at about 80 °C by passing warm water at 80 °C through the jacket, as a catalyst, phosphotungstic acid (PWA) was added in the form of a methyl formate solution at 4.5 ppm with respect to the sum of the masses of (A) and (B), or trifluoromethanesulfonic acid (TfOH) was added in the form of a cyclohexane solution at 1.0 ppm with respect to the sum of the masses of (A) and (B), and a polymerization reaction was carried out. Example 6 used TfOH, and PWA was used for the others. The component (C) used in the examples was (C-1) KR-500 (R 1 : methyl group, R 2 : methyl group), (C-2) KR-401N (R 1 : methyl group / phenyl group, R 2 : methyl group) (both manufactured by Shin-Etsu Chemical Co., Ltd.). The components of the examples and comparative examples are shown in Table 1.

[0047] After 5 minutes, 300 g of water containing 0.1% triethylamine was added to this autoclave to stop the reaction, and the content was taken out and pulverized to 200 mesh or less. After washing with acetone and drying, the polyacetal copolymer yield (the ratio of the copolymer mass obtained to the sum of the masses of (A), (B), and (C) used in the polymerization (mass%)) was calculated. The results are shown in Table 2.

[0048] For comparison, the following diglycidyl compounds (X-1 and X-2) were used in the polymerization in place of the component (C) of the present invention to obtain comparative polyacetal copolymers.

[0049] X-1: Butanediol diglycidyl ether

Chemical formula

[0050] X-2: Trimethylolpropane triglycidyl ether

Chemical formula

[0051] To 100 parts by mass of the polyacetal copolymer obtained by the above method, 0.35 part by mass of pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1010, manufactured by BASF) as a stabilizer and 0.15 part by mass of melamine were added, and melt-kneaded at 210 °C using a small twin-screw extruder to obtain a pellet-shaped polyacetal resin composition. Using these pellets, the following evaluations were carried out. The results are shown in Table 2.

[0052] <Tensile strength> In accordance with ISO 527-1 and 2, the tensile strength of an ISO Type 1A test piece was measured. The measurement chamber was maintained at an atmosphere of 23 °C and 50% RH. <Flexural strength and flexural modulus> In accordance with ISO178, the flexural strength and flexural modulus were measured. The measurement chamber was maintained at an atmosphere of 23°C and 50% RH.

[0053]

Table 1

[0054]

Table 2

[0055] In Examples 1 to 7, a polyacetal copolymer was obtained in a high yield with a low catalyst amount, and it was revealed that the polyacetal copolymer had excellent mechanical properties. In Comparative Examples 2 and 3, no polymerization reaction was observed at the same catalyst amount as in the examples. In Comparative Examples 2 and 3, when the catalyst amount was 20 ppm, a sudden violent reaction occurred, but the final yield was as low as about 50% by mass.

[0056] As is clear from the results in Table 2, according to the present invention, it is possible to provide a novel polyacetal copolymer excellent in production stability and mechanical properties and a method for producing the polyacetal copolymer.

Claims

1. A polyacetal copolymer obtained by subjecting at least trioxane (A), a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and an organopolysiloxane (C) to a polymerization reaction, wherein the organopolysiloxane (C) is a condensate of one or more silane compounds selected from the compounds represented by the following formula (1), is a compound having an alkoxy group, and is contained in an amount of 0.05 to 0.2 parts by mass based on 100 parts by mass of the trioxane (A). R １ ｎ Si(OR ２ ) ４－ｎ (1) In formula (1), R １ represents a monovalent hydrocarbon group, and R ２ represents an alkyl group having 4 or less carbon atoms. n is an integer of 0 to 2.

2. The polyacetal copolymer according to claim 1, wherein R ２ in the formula (1) is at least one selected from a methyl group and an ethyl group.

3. The polyacetal copolymer according to claim 1 or 2, wherein R １ in the formula (1) is at least one selected from a methyl group and a phenyl group.

4. A method for producing a polyacetal copolymer by subjecting at least trioxane (A), a cyclic acetal compound (B) having an oxyalkylene group having 2 or more carbon atoms in the ring, and an organopolysiloxane (C) to a polymerization reaction in the presence of a cationic polymerization catalyst, wherein the cationic polymerization catalyst is a perfluoroalkane sulfonic acid or a heteropolyacid, the organopolysiloxane (C) is a condensate of one or more silane compounds selected from the compounds represented by the following formula (1), is a compound having an alkoxy group, and is contained in an amount of 0.05 to 0.2 parts by mass based on 100 parts by mass of the trioxane (A). R １ ｎ Si(OR ２ ) ４－ｎ (1) In formula (1), R １ represents a monovalent hydrocarbon group, and R ２ represents an alkyl group having 4 or less carbon atoms. n is an integer of 0 to 2.

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