Polyacetal resin composition and medical device member

Abstract

The invention relates to a polyacetal resin composition and a medical instrument component. The purpose of the present invention is to provide: a polyacetal resin composition capable of suppressing the amount of thermal decomposition by simultaneously suppressing main chain decomposition due to an acid and terminal decomposition due to a # imgabs0 # salt during long-term storage; and a medical instrument member using the resin composition. The present invention is a polyacetal resin composition comprising a polyacetal resin and a compound (A) represented by structural formula (1), the polyacetal resin composition being characterized in that the content of the compound (A) in the composition is 1-30 ppm by mass. # imgabs1 #

Description

Technical Field

[0001] The present invention relates to a polyacetal resin composition and a medical device component, and particularly to a polyacetal resin composition and a medical device component that are not susceptible to thermal decomposition. Background Art

[0002] Polyacetal resins are materials with excellent rigidity, strength, toughness, sliding properties, and creep resistance. Therefore, polyacetal resins are used in a wide range of applications as resin materials for various mechanical components, including automotive parts, electrical and electronic components, industrial parts, and medical devices.

[0003] Polyacetal resins are known to decompose under the influence of heat, light, oxygen, acids, and alkalis. Acids are known to decompose the main chain of polyacetal resins, while alkalis are known to decompose the terminals of polyacetal resins. This decomposition is further accelerated during thermal processing of polyacetal resins, leading to deterioration in moldability and processability, and an increase in residual low-boiling-point compounds in the resulting resin molded article.

[0004] Furthermore, it is known that terminal decomposition also occurs from unstable hemiformal terminals. Therefore, these hemiformal terminals are typically stabilized for use by esterification through reaction with acetic anhydride or the like. These ester groups are known to readily decompose in the presence of a base, becoming unstable terminals. Therefore, the presence of a base in polyacetal resins is generally undesirable.

[0005] In order to improve thermal stability, various technologies have been proposed in the past.

[0006] For example, there are disclosed technologies for adding an amine polymer, polyamide, and allantoin to a polyacetal resin (see Patent Document 1), technologies for adding a poly-β-alanine polymer and polyamide 6 / 66 / 610 to a polyacetal resin (see Patent Document 2), technologies for adding a nitrogen-containing hindered phenol compound and a formaldehyde scavenger to a polyacetal resin (see Patent Documents 3, 4, and 5), and technologies for adding a polycarboxylic acid hydrazide containing an aromatic group to a polyacetal resin (see Patent Document 6).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2016 / 126514

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2009-256425

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 01-315455

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 06-179798

[0013] Patent Document 5: Japanese Patent Application Laid-Open No. 04-293952

[0014] Patent Document 6: Japanese Patent Application Laid-Open No. 2005-312801 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] In recent years, polyacetal resin compositions with further suppressed thermal decomposition amounts have been required for advanced medical device applications and the like.

[0017] However, in a general synthesis method of polyacetal resin, Salts are used as polymerization catalysts and terminal stabilization catalysts. Salts remain in the resin even after washing and drying, acting slowly as alkaline compounds, and may generate unstable ends during long-term storage, which may become the starting point of thermal decomposition. Salts and acidic compounds may also be added, but acidic compounds may cause decomposition starting from the main chain of the polyacetal resin and may accelerate the decomposition.

[0018] That is, in the conventionally known technical range, it is not possible to solve the problem of neutralizing the residual The problem that the use of salt promotes decomposition is that it is hoped that a technology that can suppress thermal decomposition can be developed.

[0019] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyacetal resin composition and a medical device component using the same, wherein the polyacetal resin composition is capable of simultaneously suppressing the main chain decomposition caused by acid and the degradation of the main chain caused by acid during long-term storage. The terminal decomposition caused by salt can suppress the amount of thermal decomposition.

[0020] Means used to solve problems

[0021] In order to solve the above problems, the present inventors have conducted intensive research and found that by adding a predetermined amount of a slowly acid-generating compound to the polyacetal resin, the acid can be neutralized without causing decomposition of the main chain. Salt, thus completing the present invention.

[0022] That is, the present invention is as follows.

[0023] [1] A polyacetal resin composition comprising a polyacetal resin and a compound (A) represented by the following structural formula (1), wherein the content of the compound (A) in the composition is 1 to 30 ppm by mass.

[0024] ···(1)

[0025] (In formula (1), R 1 、R 2 represents a hydrocarbon group having 1 to 10 carbon atoms, R 3 represents hydrogen or methyl.)

[0026] [2] The polyacetal resin composition according to [1], wherein R 3 A hydrogen atom.

[0027] [3] The polyacetal resin composition according to [1], wherein the compound (A) is methylene diacetate.

[0028] [4] A medical device component, characterized in that the medical device component comprises the polyacetal resin composition according to any one of [1] to [3].

[0029] [5] The medical device component according to [4], characterized in that the medical device component is an insulin pen syringe or a powder inhaler.

[0030] [6] Use of the polyacetal resin composition according to any one of [1] to [3] in medical device parts.

[0031] Effects of the Invention

[0032] According to the present invention, a polyacetal resin composition and a medical device component in which the amount of decomposition during thermal processing is suppressed can be provided. DETAILED DESCRIPTION

[0033] Hereinafter, a mode for implementing the present invention (hereinafter referred to as "this embodiment") will be described in detail. It should be noted that the present invention is not limited to the following description, and can be implemented with various modifications within the scope of the gist thereof.

[0034] <Polyacetal resin composition>

[0035] The polyacetal resin composition of the present embodiment contains a polyacetal resin and a compound (A) represented by the following structural formula (1).

[0036] ···(1)

[0037] (In formula (1), R 1 、R 2 represents a hydrocarbon group having 1 to 10 carbon atoms, R 3 represents hydrogen or methyl.)

[0038] The polyacetal resin composition of the present embodiment may be a composition consisting solely of the compound (A) and the polyacetal resin, or may further contain other components within a range that does not impair the effects of the present invention.

[0039] In addition, in this specification, the compound (A) represented by structural formula (1) may be simply referred to as "compound".

[0040] (Compound (A))

[0041] The polyacetal resin composition of the present embodiment contains a compound (A) represented by the following structural formula (1).

[0042] ···(1)

[0043] The compound (A) generates acid slowly, and thus can neutralize the main chain while suppressing the decomposition of the acid. Salt, as a result, can significantly reduce the amount of decomposition during thermal processing.

[0044] In the above formula (1), R 1 and R 2 The hydrocarbon group has 1 to 10 carbon atoms, and examples thereof include an alkyl group, a halogenated alkyl group, and an aryl group.

[0045] Examples of the alkyl group include alkyl groups having 1 to 10 carbon atoms, such as methyl and ethyl groups. These alkyl groups may be linear or branched, and may also include cyclic structures. Examples of the halogenated alkyl group include trichloromethyl and the like.

[0046] Examples of the aryl group include a phenyl group, a methylphenyl group, a chlorophenyl group, and a naphthyl group.

[0047] As R 3 From the viewpoint of being able to further suppress the amount of thermal decomposition, a hydrogen atom is more preferred.

[0048] Examples of the compound (A) include methylene diacetate, methylene dibutyrate, methylene dipivalate, methylene dibenzoate, ethylidene diacetate, ethylidene dibutyrate, ethylidene dipivalate, and ethylidene dibenzoate. From the viewpoint of further suppressing the amount of thermal decomposition, methylene diacetate, methylene dibutyrate, methylene dipivalate, and methylene dibenzoate are preferred, and methylene diacetate is more preferred.

[0049] In addition, the above-mentioned compounds may be used in combination of two or more.

[0050] In the polyacetal resin composition, the content of the compound (A) in the resin composition of this embodiment is 30 ppm by mass or less, preferably 10 ppm by mass or less. When the content is within the above range, main chain decomposition caused by carboxylic acid generated by decomposition can be suppressed.

[0051] In addition, in the polyacetal resin composition, the content of the compound (A) in the resin composition of this embodiment is preferably 1 mass ppm or more. By containing 1 mass ppm or more of the compound (A), the composition can be well maintained. The salt neutralization effect can inhibit the terminal decomposition of the polyacetal resin.

[0052] The compound (A) may be produced by reacting an ester compound and / or anhydride used in the polyacetal resin production step described below with formaldehyde present in the step. The thus produced compound (A) may be used directly.

[0053] The compound (A) in the resin composition of the present embodiment can be adjusted to the above-mentioned preferred content by adding a compound (A) in addition to the compound (A) generated in the production process, or by reducing the compound (A) generated in the production process by the method described below.

[0054] The method for reducing the by-product compound (A) is not particularly limited, and examples thereof include a method comprising a step (1) of removing formaldehyde under mild conditions, a step (2) of removing an ester compound and / or anhydride, and a step (3) of removing the compound (A).

[0055] In step (1), it is important to remove formaldehyde under mild conditions, such as room temperature. Under heating conditions, the aforementioned ester compound and / or acid anhydride reacts with formaldehyde, which in turn increases the amount of compound (A). Furthermore, in this step, the formaldehyde content is preferably adjusted to 10 ppm by mass or less. By adjusting the formaldehyde content to this level, the aforementioned reaction in step (2) can be suppressed, thereby inhibiting the increase in compound (A).

[0056] Specific methods are not limited to the following methods, but examples thereof include: a method in which the terminal-stabilized polyacetal resin powder is stirred and brought into contact with dry air or an inert gas at room temperature; a method in which the terminal-stabilized polyacetal resin powder is dispersed in hexane or the like to form a slurry and nitrogen is bubbled through the dispersion; a method in which the terminal-stabilized polyacetal resin powder is dispersed in hexane or the like to form a slurry and a formaldehyde scavenger is added to remove formaldehyde that can react with the ester compound and / or acid anhydride; and the like.

[0057] In step (2), it is important to remove the ester compound and / or acid anhydride at a temperature below the melting point of the polyacetal resin. At temperatures above the melting point of the polyacetal resin, the polyacetal decomposes slightly to produce formaldehyde, which triggers the aforementioned reaction to form compound (A). Furthermore, in this step, the ester compound and / or acid anhydride is preferably adjusted to 10 ppm by mass or less. By adjusting the ester compound and / or acid anhydride to this level, the aforementioned reaction in step (3) can be suppressed, thereby preventing an increase in compound (A).

[0058] Specific methods are not limited to the following methods, but include heating to a temperature lower than the melting point of the polyacetal resin using a paddle dryer equipped with a heating mechanism, and washing and removing using a low-boiling-point organic solvent capable of dissolving the ester compound and / or acid anhydride.

[0059] The step (3) of removing the compound (A) is not particularly limited, and examples thereof include a method using a dryer equipped with a heating and stirring mechanism, melt degassing using a melt kneader equipped with a vent, etc. Melt degassing is more preferred because it can efficiently remove the compound (A) remaining in the resin.

[0060] (Polyacetal resin)

[0061] The polyacetal resin contained in the polyacetal resin composition of the present embodiment has repeating oxymethylene units (acetal structures) represented by (—CH 2 O—) as main structural units, and a known polyacetal resin can be used.

[0062] The polyacetal resin contained in the polyacetal resin composition of the present embodiment may be a homopolymer composed solely of oxymethylene units, or may be a copolymer (including a block copolymer), a terpolymer, or the like containing structural units other than oxymethylene units. Furthermore, the polyacetal resin may have not only a linear structure but also a branched structure or a crosslinked structure.

[0063] In addition, the above-mentioned polyacetal resins can be used alone or in combination of two or more.

[0064] Furthermore, when the total amount of the polyacetal resin is 100% by mass, the polyacetal resin preferably contains 30% to 100% by mass of a polyacetal homopolymer, more preferably 50% to 100% by mass of a polyacetal homopolymer, and even more preferably 70% to 100% by mass of a polyacetal homopolymer.

[0065] As a method for producing the polyacetal resin, a known method can be used.

[0066] For example, polyacetal homopolymers can be obtained by polymerizing formaldehyde monomers or cyclic formaldehyde oligomers such as its trimer (trimethoxymethylene) and tetramer (tetramethoxymethylene). Furthermore, the resulting polyacetal homopolymers can be stabilized by known methods (e.g., by reacting the polymerized ends with ether groups or ester groups).

[0067] The main chain of the polyacetal homopolymer is substantially composed of only oxymethylene units, that is, preferably contains 99% by mass or more of oxymethylene units.

[0068] As the structural unit (copolymer unit) other than the oxymethylene unit in the polyacetal copolymer, an oxyethylene unit (—CH 2 CH 2 O—) is preferred.

[0069] Such polyacetal copolymers can be obtained by copolymerizing formaldehyde monomers or cyclic oligomers of formaldehyde, such as its trimers (trioxane) and tetramers (tetramethylol), with cyclic ethers such as ethylene oxide and 1,3-dioxolane. When obtaining a polyacetal copolymer from trioxane and 1,3-dioxolane, the amount of 1,3-dioxolane used is preferably 0.1 to 60 mol%, more preferably 0.1 to 20 mol%, and even more preferably 0.13 to 10 mol%, relative to 100 mol% of trioxane. The resulting polyacetal copolymer can also be stabilized by known methods (for example, by melting it with a quaternary ammonium compound and decomposing the unstable terminal portions). The polyacetal copolymer preferably contains 1 to 10% by mass of oxyethylene units, more preferably 1 to 5% by mass, and even more preferably 1 to 3% by mass, based on the entire main chain of the polymer.

[0070] From the viewpoint of achieving both fluidity and strength, the melt flow rate (MFR) of the polyacetal resin of the present embodiment is preferably 1 g / 10 min to 50 g / 10 min.

[0071] In addition, MFR can be measured under the conditions of 190°C and a load of 2.16 kg in accordance with ISO 1133-1.

[0072] In the present embodiment, the content of the polyacetal resin in 100% by mass of the polyacetal resin composition is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0073] It should be noted that, as long as the effects of the present invention are not impaired, the polyacetal resin composition of the present embodiment may contain any conventionally known additives. For example, it may contain a formic acid scavenger, a weathering stabilizer, a release agent, a lubricant, a conductive agent, a thermoplastic resin, a thermoplastic elastomer, an inorganic filler or an organic filler, a pigment, a dye, and other known additives. These additives may be used alone or in combination of two or more.

[0074] The polyacetal resin composition of the present embodiment can be produced by, for example, a known melt-kneading method.

[0075] For example, the polyacetal resin and the compound may be mixed using a mixer such as a Henschel mixer, and then supplied to a single-screw or twin-screw melt-kneading device (extruder) for melt-kneading. Alternatively, the polyacetal resin may be supplied upstream of a single-screw or twin-screw extruder to be molten, and then the compound may be supplied downstream for melt-kneading.

[0076] <Moldings, Medical Device Parts>

[0077] The molding method of the polyacetal resin composition of this embodiment is not particularly limited, and examples thereof include well-known molding methods, such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, heterogeneous material molding, gas-assisted injection molding, foam injection molding, low-pressure molding, ultra-thin-wall injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, injection molding on substrate), meltblown molding, etc.

[0078] The shape of the molded article is not particularly limited, and examples thereof include injection molded articles (including on-substrate injection molded articles and insert molded articles), fibers / non-woven fabrics, sheets / films, and profile extruded articles.

[0079] The use of the molded body is not particularly limited. For example, it can be suitably used in mechanical parts represented by gears, cams, sliders, rods, shafts, bearings and guides; automobile interior parts represented by door peripheral parts, seat belt peripheral parts, combination switch parts, and switches; and especially medical equipment parts represented by insulin pen syringes, powder inhaler mechanical parts, infusion pump stopcocks, etc.

[0080] The polyacetal resin composition of this embodiment can suppress the decomposition of the main chain caused by the carboxylic acid generated by decomposition by containing a specific amount of compound (A). In addition, compound (A) gradually decomposes and neutralizes As a result, the polyacetal resin composition of the present embodiment can highly suppress the amount of formaldehyde generated both in an inert gas environment and in air, and can therefore be suitably used for medical device parts.

[0081] Example

[0082] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0083] The raw material components used in Examples and Comparative Examples are as follows.

[0084] (1) Polyacetal resin:

[0085] (POM-1) Polyacetal copolymer obtained by polymerizing trioxymethylene and 1,3-dioxolane (MFR=25)

[0086] (POM-2) Polyacetal homopolymer obtained by polymerizing formaldehyde (MFR=23.5)

[0087] The MFR value was measured using a MELTINDEXER manufactured by Toyo Seiki Co., Ltd. at a cylinder temperature of 190° C. and a load of 2.16 kg in accordance with ISO 1133-1.

[0088] POM-2 used a material containing 200 ppm by mass of methylene diacetate produced as a by-product in its production process.

[0089] (POM-3) Polyacetal homopolymer obtained by polymerizing formaldehyde (MFR=21.9)

[0090] The MFR value was measured using a MELTINDEXER manufactured by Toyo Seiki Co., Ltd. at a cylinder temperature of 190° C. and a load of 2.16 kg in accordance with ISO 1133-1.

[0091] POM-3 used was a powdered product before melt-kneading containing 50 ppm by mass of methylene diacetate produced as a by-product in its production process, 65 ppm by mass of unreacted acetic anhydride, and 1000 ppm by mass of formaldehyde.

[0092] (2) Compounds

[0093] (Compound 1) Methylene diacetate (manufactured by Combi-Blocks)

[0094] (Compound 2) Ethylene diacetate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0095] (Compound 3) Methylene dibenzoate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0096] (Compound 4) Acetic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0097] <Examples 1 to 5, Comparative Examples 1 to 5, Comparative Example 8, Comparative Example 9>

[0098] The polyacetal resin and each compound were mixed in the amounts shown in Table 1, fed into a twin-screw extruder (PCM30 manufactured by Ikegai), melt-kneaded at a screw speed of 60 rpm and a barrel set temperature of 200°C, and then pelletized to obtain resin compositions of each sample.

[0099] Note that all samples used the aforementioned POM-1 as the polyacetal resin. For Comparative Example 1, no compound was added, and only the polyacetal resin was supplied, and granulation was performed under the aforementioned conditions. The resulting pellets were dried in a hot air dryer at 80°C for 3 hours.

[0100] [Table 1]

[0101]

[0102] <Example 6>

[0103] The polyacetal resin used was the aforementioned POM-3, which contained 50 mass ppm of methylene diacetate, a by-product of the production process, 65 mass ppm of unreacted acetic anhydride, and 1000 mass ppm of formaldehyde. Dry air was blown through the mixture while stirring at room temperature to reduce the formaldehyde content to 9 mass ppm. The mixture was then heated to 130°C in a paddle dryer to reduce the acetic anhydride content to 3 mass ppm. The mixture was then dried in a hot air dryer at 80°C for 10 hours to reduce the methylene diacetate content to 27 mass ppm. The mixture was then pelletized using a mixer.

[0104] <Comparative Example 6>

[0105] As the polyacetal resin, the above-mentioned POM-2 containing 200 ppm by mass of methylene diacetate produced as a by-product in the production process was used, and the resulting resin was dried in a hot air dryer at a temperature of 80° C. for 10 hours.

[0106] <Comparative Example 7>

[0107] The polyacetal resin used was POM-3 containing 50 ppm by mass of methylene diacetate by-produced in the production process, 65 ppm by mass of unreacted acetic anhydride, and 1000 ppm by mass of formaldehyde. The resin was dried in a hot air dryer at 80°C for 10 hours and then pelletized using a kneader.

[0108] <Evaluation>

[0109] The samples obtained in Examples and Comparative Examples were measured and evaluated as follows. The results are shown in Table 2.

[0110] (1) Thermal decomposition amount

[0111] The thermal decomposition amount of the polyacetal resin composition was measured using a thermogravimetric analyzer (TGA) apparatus (Thermoplus EVO2 manufactured by Rigaku Corporation) at 200° C. for 100 minutes, and the thermal weight loss (% by weight) was determined.

[0112] The heat loss was measured under both nitrogen and air conditions, and the results are shown in the table. A smaller value indicates that the thermal decomposition is more suppressed, which is preferable.

[0113] (2) Amount of compound in the resin composition

[0114] 2g of each resin composition sample and 10g of purified water were placed in a sealed container and heated in an oven at 37°C for 24 hours. After returning to room temperature, the particles and solution were separated by natural filtration. The solution was analyzed using GC (equipment: Shimadzu GC-2014ATF-SPL, column: Shimadzu GLC SH-PolarWax) to determine the amount of compound dissolved in the solution. The amount of compound in the resin is expressed as the amount of compound by mass (ppm) relative to the polyacetal resin.

[0115] [Table 2]

[0116]

[0117] As can be seen from Table 2, the resin composition samples of the examples were able to reduce the amount of thermal decomposition under air, particularly, compared with the resin composition samples of the comparative examples.

[0118] Industrial Applicability

[0119] The polyacetal resin composition of the present invention can be suitably used in fields such as automotive interior applications and medical equipment applications, which require reduction of volatile organic compounds.

Claims

1. A polyacetal resin composition comprising a polyacetal resin and a compound (A) represented by the following structural formula (1), characterized in that: The content of the compound (A) in the composition is 1 ppm by mass to 30 ppm by mass. ···（1） In formula (1), R 1 、R 2 represents a hydrocarbon group having 1 to 10 carbon atoms, R 3 represents hydrogen or methyl.

2. The polyacetal resin composition according to claim 1, wherein The compound (A) R 3 A hydrogen atom.

3. The polyacetal resin composition according to claim 1, wherein The compound (A) is methylene diacetate.

4. A medical device component, characterized in that: The medical device component comprises the polyacetal resin composition according to any one of claims 1 to 3.

5. The medical device component according to claim 4, characterized in that The medical device component is an insulin pen syringe or a powder inhaler.

6. Use of the polyacetal resin composition according to any one of claims 1 to 3 in medical device parts.

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