JP2005132896A - Polyoxymethylene resin vacuum molded article and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum molded article which comprises a polyoxymethylene resin, is little distorted, and has a desired shape. <P>SOLUTION: This polyoxymethylene resin vacuum molded article comprises a polyoxymethylene copolymer which contains oxyalkylene units represented by the general formula (1) [R<SB>1</SB>and R<SB>2</SB>are each identically or differently selected from H, a 1 to 8C alkyl, a 1 to 8C alkyl group-having organic group, phenyl, and a phenyl group-having organic group; (m) is an integer of 2 to 6] in an amount of 1.5 to 10 moles per 100 moles of oxymethylene units in a polymer chain consisting mainly of repeating oxymethylene units and has a melt index (190°C, a load of 2,160g) of 0.3 to 20 g/10 min. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vacuum-formed product comprising a specific polyoxymethylene copolymer, having excellent mechanical properties, thermal properties, chemical properties, low distortion and excellent dimensional accuracy, and a method for producing the same. is there.

  A vacuum forming method is generally known as a method for processing a resin material into a container shape, a box shape or the like. Such a vacuum forming method is performed as follows, for example. That is, a resin sheet is prepared in advance by a method such as heating, melting, and kneading the resin material with an extruder, extruding into a flat plate shape through a die provided at the exit of the extruder, and solidifying by cooling. Clamping on a mold and heat-softening, and vacuuming between the mold and the sheet allows the softened sheet to be in close contact with a mold having a desired shape, and then cooled and solidified to achieve the desired molding To get goods.

  Conventionally, the material of such a vacuum-formed product has been limited to resins having low crystallinity such as polyolefin, polyester, and polystyrene.

  However, since the above resin has low crystallinity, the strength of the molded product is limited, and the rigidity at high temperature is insufficient, so that it can sufficiently meet the recent demand for higher strength vacuum molded products. There were cases where it was not possible.

  In contrast, a polyoxymethylene resin having a polymer skeleton mainly composed of repeating oxymethylene units is known to have high crystallinity and excellent rigidity, strength, chemical resistance, solvent resistance, and the like. Because of its high crystallization speed and fast molding cycle, it is widely used as an injection molding material in the field of mechanical parts for automobiles and electrical equipment.

  Thus, although polyoxymethylene resin is a resin having excellent properties, polyoxymethylene resin has a high degree of crystallinity and a high solidification rate. It is difficult to make the product flexible, and even when the sheet is formed in close contact with the mold by vacuum suction, the difference in thickness depending on the shape and location of the molded product, and the contact behavior to the mold. (So early and late of contact) and the like, cooling solidification becomes uneven, and it was extremely difficult to accurately transfer the mold shape to the sheet to form a molded product having the desired shape.

  For this reason, vacuum forming using a polyoxymethylene resin has hardly been performed in the past, and this behavior in the vacuum forming of a polyoxymethylene resin is essentially as described above for a polyoxymethylene resin. Because of its nature, it has been considered difficult to improve it to be suitable for vacuum forming, and it has hardly been studied.

  For this reason, when the present inventor conducted a patent investigation from the viewpoint of vacuum forming using a polyoxymethylene resin and a composition thereof, the inventors could not find anything considered to be equivalent to the prior art of the present invention.

  An object of the present invention is to solve the above-described problems, and to provide a vacuum molded product made of a polyoxymethylene resin and having a desired shape with a small distortion and a production method with high productivity.

  As a result of diligent research to achieve the above object, the inventors of the present invention have improved workability in vacuum molding by using a specific polyoxymethylene copolymer with controlled crystallinity and solidification rate, and a mold. The present inventors have found that an excellent molded product with good transferability and little molding distortion can be obtained, and have reached the present invention.

  That is, the present invention includes a polymer chain composed mainly of repeating oxymethylene units, containing 1.5 to 10 mol of oxyalkylene units represented by the following general formula (1) per 100 mol of oxymethylene units, and having a melt index (190 ° C., load 2160 g) a polyoxymethylene resin vacuum-molded product comprising a polyoxymethylene copolymer having a weight of 0.3 to 20 g / 10 min.

(Wherein, R _1, R ₂ is hydrogen, an alkyl group having 1 to 8 carbon atoms, an organic group having an alkyl group of 1 to 8 carbon atoms, a phenyl group, selected from an organic group having a phenyl group, R ₁ R ₂ may be the same or different, and m represents an integer of 2 to 6.)
And it is a manufacturing method of the vacuum formed goods characterized by using the above-mentioned polyoxymethylene copolymer.

  Hereinafter, the present invention will be described in detail. First, the polyoxymethylene copolymer used in the polyoxymethylene resin vacuum-formed product of the present invention and the production method thereof will be described.

  In the vacuum molded product and the method for producing the same of the present invention, the polymer chain mainly composed of repeating oxymethylene units contains 1.5 to 10 mol of the oxyalkylene unit represented by the general formula (1) per 100 mol of oxymethylene units. A polyoxymethylene copolymer is used.

  In the polyoxymethylene copolymer used in the present invention, the ratio of the oxyalkylene unit represented by the general formula (1) needs to be 1.5 to 10 mol per 100 mol of the oxymethylene unit, preferably the oxymethylene unit. 2 to 8 mol per 100 mol, particularly preferably 2 to 5 mol per 100 mol of oxymethylene units. When the proportion of the oxyalkylene unit represented by the general formula (1) is reduced, the polyoxymethylene copolymer has a high degree of crystallinity and a solidification speed, and the softened sheet is molded by vacuuming during vacuum molding. Since the shape fixing starts before being pressed into the mold shape, the desired shape cannot be obtained. Also, due to the rapid solidification rate, the solidification behavior becomes non-uniform due to the thickness of the molded product and the early and late adhesion to the mold, and the strain in the molded product generated during the solidification process increases. The obtained molded product may have a deformed shape. Conversely, when the proportion of the oxyalkylene unit represented by the general formula (1) is increased, the degree of crystallinity of the polyoxymethylene copolymer is lowered, and the molded product made of such a copolymer is inferior in heat resistance, The strength, elastic modulus and the like are also low.

  In the present invention, the reason why the vacuum formability is excellent due to the use of a specific polyoxymethylene copolymer is not necessarily clear, but the present inventor generally estimates as follows.

  First, in vacuum forming, the raw sheet is heated to near the crystal melting temperature of the resin, so that the molecular mobility of the resin that forms the sheet is increased, and this is pressed against the mold while being sucked into vacuum. Then, it is formed by cooling. The specific polyoxymethylene copolymer used in the present invention has a moderately reduced degree of crystallinity, which increases the proportion of molecular chains with high mobility. The shape tends to be easily transferred. In the process of obtaining the desired molded product by reducing the molecular mobility by cooling after mold shape transfer and fixing the shape, the specific polyoxymethylene resin used in the present invention has a reasonably slow decrease in molecular mobility due to cooling. Therefore, it has excellent transferability by lowering molecular mobility after transfer of a sufficient mold shape, and it is easy to relieve internal strain generated during molding by molecular motion, so that a molded product with less deformation can be obtained. Can do. The specific polyoxymethylene resin used in the present invention is presumed to have an excellent molded product due to its high molecular mobility.

  Further, the polyoxymethylene copolymer used in the present invention is required to have a melt index (MI) of 0.3 to 20 g / 10 min measured at 190 ° C. under a load of 2160 g in accordance with ASTM D-1238. Yes, preferably 0.5 to 10 g / 10 min, particularly preferably 0.5 to 5 g / 10 min. If the melt index (MI) is too small, the load at the time of melt extrusion during the production of the raw sheet increases, making extrusion difficult. Conversely, if the melt index (MI) is too large, the resulting molded product becomes brittle and tough. Tends to decrease, and there is a tendency that sufficient strength cannot be obtained in practical use.

  The production method of the polyoxymethylene copolymer as described above used in the present invention is not particularly limited. Generally, trioxane and a cyclic ether compound or cyclic formal compound as a comonomer are mainly used as a cationic polymerization catalyst. It can be obtained by a bulk polymerization method. As the polymerization apparatus, any known apparatus such as a batch system or a continuous system can be used. Here, the introduction ratio of the oxyalkylene unit represented by the general formula (1) is adjusted by the amount of the comonomer to be copolymerized. The melt index (MI) can be adjusted by the amount of chain transfer agent used during polymerization, such as methylal.

  The melt index of the copolymer obtained is small when the addition amount of the chain transfer agent is decreased, and is increased when it is increased. The melt index is affected by impurities such as water and methanol contained in the raw material monomer and comonomer, and the type, shape, size, and polymerization conditions of the polymerization machine. It is difficult to unambiguously determine the absolute amount of chain transfer agent necessary to obtain a coalescence, and while trying to produce a copolymer, the chain transfer agent can be obtained so that the desired melt index is obtained. Increase or decrease the amount added.

  Examples of cyclic ether compounds or cyclic formal compounds used as comonomers include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, oxetane, tetrahydrofuran, trioxepane, 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, etc., among which ethylene oxide, 1,3-dioxolane, diethylene glycol formal, and 1,4-butanediol formal are preferable. The polyoxymethylene copolymer used in the present invention may have a branched or crosslinked structure. For this purpose, a small amount of a monofunctional or bifunctional or higher glycidyl compound other than those described above is added to the copolymer. It may be polymerized.

  The polyoxymethylene copolymer obtained by polymerization is subjected to catalyst deactivation treatment, removal of unreacted monomers, polymer washing, drying, stabilization of unstable terminal portions, etc., and various stabilizers. It is provided for practical use by performing a stabilization treatment or the like by blending. Representative stabilizers include hindered phenol compounds, nitrogen-containing compounds, alkali or alkaline earth metal hydroxides, inorganic acid salts, carboxylate salts, and the like.

  In the polyoxymethylene copolymer used in the present invention, general additives for thermoplastic resins, for example, coloring agents such as dyes and pigments, lubricants, nucleating agents, mold release agents, antistatic agents are used as necessary. One or more surfactants, organic polymer materials, inorganic or organic fibrous, plate-like, and powdery fillers can be added as long as the object of the present invention is not impaired. .

  Next, a method for producing a vacuum formed product using the above polyoxymethylene copolymer will be described. Vacuum forming is basically performed as follows. That is, after the resin is heated and melted in an extruder having a single screw or a twin screw, the molten resin is extruded from an extrusion molding die (T-die, etc.) and wound with a cooling roll to have a thickness of about 0.2 mm to 1 mm. After forming the sheet, vacuum forming is performed continuously or discontinuously. In vacuum forming, the sheet is heated below the melting point by a non-contact or contact type far-infrared plate heater or hot air heating method and pressed against a mold having a desired shape with vacuum holes while sucking in vacuum. After shaping, the desired shape is obtained by cooling and solidifying. The heating temperature of the raw sheet is preferably (resin melting point−40) ° C. or higher and melting point or lower.

  Further, the present invention is preferably applied to a vacuum molded product having a drawing ratio of 0.01 to 1.0.

  As the shape of the obtained vacuum molded product, a container-like shape is common. In addition, although the general method about the vacuum forming method was shown here, the manufacturing method of the vacuum-formed product made from polyoxymethylene resin of this invention is not limited to the method described here.

  The vacuum-formed product made of polyoxymethylene resin of the present invention has various uses by taking advantage of its excellent properties such as high strength, high elastic modulus, solvent resistance, heat resistance, fatigue resistance, alkali resistance, and high temperature rigidity. . For example, it can be used for heat-resistant containers, molds for various modeling materials (concrete, mortar, synthetic resin, plaster), blisters, trays, packages, building materials, and other various uses.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
Examples 1-7
Two with paddles using a continuous mixing reactor composed of a barrel that has a shape with two circular cross-sections and a rotating shaft with paddles. While rotating the rotating shaft of each at 150 rpm, liquid trioxane, cyclic ether or cyclic formal as a comonomer, methylal as a molecular weight regulator, and 50 ppm of boron trifluoride (based on all monomers) at the same time are added to the polymerization machine. Bulk polymerization was performed while continuously feeding. Table 1 shows the water content of the trioxane used, the kind of comonomer, and the amount of methylal (ratio to the total monomer weight). The water content of the comonomer was 40 ppm or less. The amount of methylal added was finely adjusted within the range shown in Table 1 according to the target value of the melt index of the obtained copolymer.

  While rapidly passing the reaction product discharged from the polymerization machine through a crusher, the catalyst was deactivated by adding it to a 60 ° C. aqueous solution containing 0.05% by weight of triethylamine. Further, after separation, washing and drying, a crude polyoxymethylene copolymer was obtained. Table 2 shows the properties of the obtained copolymer.

  Next, 4 parts by weight of a 5% by weight aqueous solution of triethylamine and pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) are added to 100 parts by weight of the crude polyoxymethylene copolymer. ) Propionate] was added in an amount of 0.3 parts by weight, and the mixture was melt kneaded at 210 ° C. with a twin screw extruder to remove unstable parts.

  To 100 parts by weight of the polyoxymethylene resin obtained by the above method, 0.03 part by weight of pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] as a stabilizer and melamine 0.15 part by weight was added and melt-kneaded at 210 ° C. with a twin-screw extruder to obtain a pellet-shaped polyoxymethylene resin.

Using the pellet-shaped polyoxymethylene resin obtained above, the resin was melt plasticized by an extruder with a cylinder setting temperature of 200 ° C., extruded from a T-die, and wound with a cooling roll to form a 0.5 mm thick sheet. Obtained. Next, the sheet was heated to a temperature shown in Table 2 with a far-infrared plate heater, and then the sheet was pressed against a mold having vacuum holes while depressurizing to obtain a circular container having a depth of 20 mm and an inner diameter of 150 mm. Table 2 shows the results of evaluation by the evaluation method described later.
Comparative Examples 1-4
Except for changing the amount of comonomer used or the amount of methylal as shown in Table 1, polyoxymethylene (co) polymers outside the scope of the present invention as shown in Table 2 were prepared in the same manner as in the Examples. The amount of methylal added was finely adjusted within the range shown in Table 1 according to the target value of the melt index. In Comparative Example 4, methylal was not added to obtain a copolymer having a low melt index.

The obtained (co) polymer was subjected to stabilization treatment and the like in the same manner as in Examples, and further subjected to vacuum extrusion to obtain a molded product. Table 2 shows the results of evaluation by the evaluation method described later.
Example 8
A crude polyoxymethylene copolymer having a branched structure as shown in Table 3 was polymerized in the same manner as in Example 1 except that n-butylglycidyl ether was added as a copolymerization component together with 1,3-dioxolane. Got. Further, after performing the same treatment as in Example 1, vacuum extrusion molding was performed to obtain a molded product similar to that in Example 1. Table 3 shows the results of evaluation by an evaluation method described later.

In addition, the evaluation criteria etc. in an Example and a comparative example are as follows.
[Melt index (MI) measurement]
According to ASTM D-1238, measurement was performed at 190 ° C. under a load of 2160 g.
[Polymer composition analysis]
The polymer used for the physical property evaluation was dissolved in hexafluoroisopropanol d2, and ¹ H-NMR measurement was performed. It quantified from the peak area corresponding to each unit. In the table, the ratio of copolymerized units is shown in mol ratio per 100 mol of oxymethylene units.
[Shape judgment]
Whether or not the desired shape was obtained was visually observed and judged according to the following criteria.
3 points ... A desired shape is obtained.
2 points ... Although the desired shape is almost obtained, a slightly defective part (unevenness or defective shape of the mold shape) is recognized.
1 point ... The desired shape cannot be obtained and cannot be processed.

Claims (14)

The polymer chain mainly composed of repeating oxymethylene units contains 1.5 to 10 mol of oxyalkylene units represented by the following general formula (1) per 100 mol of oxymethylene units, and has a melt index (190 ° C., load 2160 g) of 0.3 to A vacuum-formed product made of polyoxymethylene resin comprising a polyoxymethylene copolymer of 20 g / 10 min.

(Wherein, R _1, R ₂ is hydrogen, an alkyl group having 1 to 8 carbon atoms, an organic group having an alkyl group of 1 to 8 carbon atoms, a phenyl group, selected from an organic group having a phenyl group, R ₁ R ₂ may be the same or different, and m represents an integer of 2 to 6.) The polyoxymethylene resin vacuum-formed product according to claim 1, wherein the polyoxymethylene copolymer contains 2 to 8 mol of the oxyalkylene unit per 100 mol of oxymethylene unit. 2. The vacuum molded article made of polyoxymethylene resin according to claim 1, wherein the polyoxymethylene copolymer contains 2 to 5 mol of the oxyalkylene unit per 100 mol of oxymethylene unit. The polyoxymethylene resin vacuum molded article according to any one of claims 1 to 3, wherein the polyoxymethylene copolymer has a melt index of 0.5 to 10 g / 10 min. The polyoxymethylene resin vacuum molded article according to any one of claims 1 to 3, wherein the polyoxymethylene copolymer has a melt index of 0.5 to 5 g / 10 min. The polyoxymethylene copolymer vacuum-molded product according to any one of claims 1 to 5, wherein the polyoxymethylene copolymer has a branched or crosslinked structure. The drawing ratio is from 0.01 to 1.0. The polyoxymethylene resin vacuum-formed product according to any one of claims 1 to 6. In the production of a vacuum-formed product comprising a polyoxymethylene resin, 1.5 to 10 mol of an oxyalkylene unit represented by the following general formula (1) per 100 mol of oxymethylene units is contained in a polymer chain mainly composed of repeating oxymethylene units. A polyoxymethylene resin vacuum-molded product manufacturing method comprising using a polyoxymethylene copolymer having a melt index (190 ° C., load 2160 g) of 0.3 to 20 g / 10 min.

(Wherein, R _1, R ₂ is hydrogen, an alkyl group having 1 to 8 carbon atoms, an organic group having an alkyl group of 1 to 8 carbon atoms, a phenyl group, selected from an organic group having a phenyl group, R ₁ R ₂ may be the same or different, and m represents an integer of 2 to 6.) The method for producing a polyoxymethylene resin vacuum-formed product according to claim 8, wherein the polyoxymethylene copolymer contains 2 to 8 mol of the oxyalkylene unit per 100 mol of the oxymethylene unit. The method for producing a polyoxymethylene resin vacuum-formed product according to claim 8, wherein the polyoxymethylene copolymer contains 2 to 5 mol of the oxyalkylene unit per 100 mol of oxymethylene unit. The method for producing a polyoxymethylene resin vacuum-formed product according to any one of claims 8 to 10, wherein the polyoxymethylene copolymer has a melt index of 0.5 to 10 g / 10 min. The method for producing a polyoxymethylene resin vacuum molded article according to any one of claims 8 to 10, wherein the polyoxymethylene copolymer has a melt index of 0.5 to 5 g / 10 min. The method for producing a vacuum-formed product made of a polyoxymethylene resin according to any one of claims 8 to 12, wherein the polyoxymethylene copolymer has a branched or crosslinked structure. The raw sheet made of a polyoxymethylene copolymer is heated to (melting point of resin −40) ° C. or higher and lower than or equal to the melting point and vacuum-molded, to form a poly according to claim 8. Manufacturing method of vacuum molded product made of oxymethylene resin.