JPH0680795A - Biaxially oriented polyoxymethylene film - Google Patents

Abstract

PURPOSE:To provide the title film greatly improved in stability in biaxial orientation and excellent in the characteristics, such as mechanical characteristics, with little loss of excellent characteristics inherent in polyoxymethylene. CONSTITUTION:The film consists of 50-99 pts.wt. polyoxymethylene polymer of which the major part of the principal chain consists substantially of repeating oxymethylene groups, -(CH2-O)-, and 50-1 pt.wt. polyvinylphenol resin or derivative thereof.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention comprises a polyoxymethylene polymer whose main chain is essentially composed of repeating units of an oxymethylene group-(CH2-0)-and a polyvinylphenol resin or a derivative thereof. A biaxially stretched polyoxymethylene film constructed.

[0002]

It is well known that polyoxymethylene is a highly crystalline polymer. Polyoxymethylene films can be obtained by, for example, melt pressing or melt extrusion, followed by quenching, but the films obtained by these methods are opaque or translucent and have poor mechanical properties. This is said to be because the crystallized polyoxymethylene forms a highly developed spherulite structure. Therefore, attempts have been made to improve such characteristics by biaxially stretching polyoxymethylene.

JP-A-61-252135 and 61
-286115 and 62-13318 disclose that a polyoxymethylene film highly biaxially oriented and crystallized by biaxial stretching has a high tensile elastic modulus and excellent dimensional stability, and further industrial production thereof. A method is also disclosed. In order to bring out its excellent characteristics by biaxially stretching polyoxymethylene, it is preferable to set a higher draw ratio in two directions (normally a draw ratio of 5 times or more is preferred in each direction).

However, in biaxially stretching polyoxymethylene, it was difficult to stretch to a desired stretching ratio unless the temperature was very close to the melting point because of its high crystallinity.
Therefore, in order to perform stable stretching, it is required to control the conditions such as the stretching temperature and the stretching speed accurately and uniformly in this temperature range. However, considering the production of a film with a higher draw ratio and maintaining a high yield at the time of its production, the control of the stretching conditions is not yet at a sufficient level, and a new measure for more stable stretching is proposed. Wanted

[0005]

SUMMARY OF THE INVENTION The present invention overcomes these problems, greatly improves the stretching stability, and does not impair the excellent properties of polyoxymethylene,
It is intended to provide a biaxially stretched polyoxymethylene film having excellent properties.

[0006]

Due to the high crystallinity of polyoxymethylene, few resins compatible with it are known. Therefore, there have been few reports on mixed systems, most of them related to blending with thermoplastic elastomers such as polyurethane, and these were related to incompatible systems. Recently, it has been reported that novolac type phenolic resin is compatible with polyoxymethylene (Polymer Papers, vol. 48, 7, 443 (199).
1)).

The present inventors have paid attention to polyvinylphenol having the same phenol group and its polymer, and have earnestly studied the compatibility and kneadability with polyoxymethylene.
As a result, it was discovered that polyvinylphenol was extremely compatible with polyoxymethylene and its polymer.
Therefore, biaxial stretching was attempted for a mixture obtained by melt-kneading this resin with polyoxymethylene. As a result, they have found that the stretching is much more stable than the conventional one, the temperature range of the stretching can be set wider than the conventional one, and the stretching performance is greatly improved, and the present invention has been accomplished.

That is, in the present invention, 50 to 99 parts by weight of a polyoxymethylene polymer in which the main part of the main chain is substantially composed of repeating units of oxymethylene group-(CH ₂ --O)-and polyvinylphenol resin Or its derivative 50-
And a biaxially stretched polyoxymethylene film containing 1 part by weight. The present invention will be described in detail below.

Polyvinylphenol is extremely compatible with polyoxymethylene and its polymers. Further, when biaxial stretching was tried on the mixture obtained by kneading, it was found that the stretching was significantly more stable than the conventional one, and depending on the composition, it could be easily stretched at a temperature lower than the conventional stretching temperature by a few degrees to 10 degrees Celsius. . As a result, the stretching temperature can be easily controlled and stable stretching can be performed. Since it is possible to stretch at a lower temperature, it is possible to bring out excellent properties such as high mechanical strength even at a low stretch ratio due to the stronger orientation of the polyoxymethylene molecular chain during stretching. It was

The polyvinylphenol of the present invention is usually a polymer of p-vinylphenol having a vinyl group at the para position, and has a usual number average molecular weight of 1 represented by the general formula of the following chemical formula 1.
It is a high molecular weight polymer of 000 to 5000. In Chemical formula 1, R = H is generally common, but an alkyl group-substitution type such as methylation or t-butylation, or one in which a plurality of these substituents are substituted may be used.

[0011]

[Chemical 1]

Furthermore, derivatives thereof copolymerized with various monomers are also applicable to the present invention. For example, a styrene copolymer represented by the following chemical formula 2 and a methyl methacrylate copolymer represented by the following chemical formula 3 can be applied.

[0013]

[Chemical 2]

[0014]

[Chemical 3]

Further, derivatives such as 2-hydroxyethyl acrylate copolymer, 2-hydroxyethyl methacrylate copolymer, butyl acrylate copolymer and the like can be applied. In each of the above copolymers, the composition ratio of vinylphenol and the copolymerization monomer is not particularly limited, but the molar ratio of vinylphenol / copolymerization monomer is 30/70 or more,
It is more preferably 50/50 or more, that is, the ratio of vinylphenol is high.

If polyvinylphenol or its derivative contains a free phenolic compound as an impurity, the thermal stability of polyoxymethylene may be impaired in some cases, so these should be removed as much as possible. preferable. Preferably, these residual phenolic compounds are 1% by weight or less, more preferably 0.1% by weight or less. Further, since the thermal stability of polyoxymethylene may be impaired similarly when a metal component such as a metal ion is contained, it is preferable to remove these metal components as much as possible.

The polyoxymethylene of the present invention is a polyoxymethylene polymer in which the main part of the main chain is substantially composed of repeating units of oxymethylene groups. For example, a polyoxymethylene homopolymer obtained by polymerizing formaldehyde or a cyclic oligomer of formaldehyde, such as trioxane and tetraoxane, the main chain of which consists mostly of oxymethylene chains, but of ethylene oxide or 1,3-dioxolane There is a polyoxymethylene copolymer obtained by adding 0.1 to 15 mol% of a cyclic ether having at least two adjacent carbon atoms to trioxane and polymerizing.

The copolymer may be obtained, for example, by copolymerizing at least one polyfunctionally reactive compound copolymerizable with trioxane and at least one monofunctionally reactive compound copolymerizable with trioxane. Copolymers such as trioxane, 1,4-butanediol diglycidyl ether or bis (1,2,5-
Examples thereof include a copolymer obtained by copolymerizing pentanetriol) -triformal and ethylene oxide. This copolymer forms a polymer whose molecular chain is not linear but branched or networked. The present invention is also applicable to the above homopolymers and copolymers, and also to a mixture obtained by mixing the homopolymer and the copolymer in an appropriate ratio.

Further, the main part of the main chain is substantially composed of an acetalized product of polyoxymethylene, a reaction product with isocyanate, or a small amount of a third component, for example, a copolymer obtained by copolymerizing an alkyl group such as stearyl group. The present invention can be applied to any polyoxymethylene polymer composed of repeating units of oxymethylene groups. The present invention is a composition comprising 50 to 99 parts by weight of polyoxymethylene and 50 to 1 parts by weight of the above-mentioned polyvinylphenol or its derivative. In order not to impair the excellent properties inherently possessed by polyoxymethylene as much as possible, and in order to exhibit more excellent effects by adding and mixing these,
In the present invention, the suitable composition ratio of polyvinylphenol is 30 parts by weight or less, more preferably 20 parts by weight or less. On the other hand, the lower limit is 1 part by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more. Further, within the scope of the present invention, of course, the present invention also includes a mixture obtained by adding and mixing a mixture obtained by mixing the above-mentioned polyvinylphenol and its derivative with polyoxymethylene.

The composition of the present invention limits the composition ratio of polyoxymethylene and polyvinylphenol or a derivative thereof. In addition to these components, a third component, an additive and the like may be added, if necessary. It can be added and mixed. For example, various additives such as hindered phenol-based antioxidants or polyamide-based heat stabilizers are usually used for polyoxymethylene for the purpose of improving the thermal stability. In the present invention, these various additives are used. May be included.

The method for producing the biaxially stretched polyoxymethylene film of the present invention is described in JP-A-61-252135.
No. 61-286115, No. 62-133.
No. 18, Japanese Patent Laid-Open No. 1-80514, No. 1-28.
No. 6820 and No. 2-70422. The present invention is not particularly limited to these, but can be cited as suitable examples. As a specific example, the polyoxymethylene composition of the present invention is melt-extruded and formed into a sheet or film (hereinafter referred to as a raw fabric). Next, this raw fabric is rolled by a roll mill. The rolling at this time is performed by setting the reduction ratio r to r = 1-t / t.
₀ (t ₀ and t represent the thickness of the material before and after rolling)
In this case, the range of 1.2 ≦ 1 / (1-r) ≦ 5 is preferable. Then, a biaxially stretched film can be produced by introducing the film into a transverse stretching machine and then a longitudinal stretching machine to perform transverse stretching and longitudinal stretching, respectively. At this time, the transverse stretching ratio is preferably 5 times or more, and the longitudinal stretching ratio is preferably 5 (1-r) times or more. Further, if necessary, in order to improve the mechanical properties and the like, it is possible to perform stretching again in the machine direction and / or the transverse direction.
Further, in order to improve dimensional stability, heat treatment can be performed after biaxial stretching.

[0022]

The present invention will be described in more detail with reference to examples. The melting points and tensile elastic moduli shown in the examples were measured by the following methods. (1) Melting point Differential running calorimeter (DSC) [Seiko Wu Denshi Kogyo Co., Ltd.]
Manufactured by DSC200], a sample melting curve was obtained at a sample weight of 10 mg and a temperature rising rate of 10 ° C./min, and the peak temperature of this melting curve was taken as the melting point. (2) Tensile elastic modulus A test piece with a length of 100 mm and a width of 10 mm is placed between the chucks 60.
mm, strain rate 50% / min, temperature 23
A stress-strain curve was obtained at a temperature of 50 ° C and a humidity of 50%, and the tensile modulus was calculated from the initial gradient of this curve.

[0023]

Example 1 and Comparative Example 1 Polyoxymethylene homopolymer [Tenac # 3010 grade manufactured by Asahi Chemical Industry Co., Ltd.] and polyvinyl phenol resin [Maruzen Petrochemical Co., Ltd.]
Maruka Linker M-S2] having the composition shown in Table 1 were mixed in a drum blender, and each mixture was melt-kneaded at 200 ° C. by a screw type twin-screw extruder to form pellets.

Next, each of the mixed and homogenized pellets was extruded from a slit die at a temperature of 200 ° C. and 130 ° C.
800 μm thick after being rapidly cooled and solidified with a casting roll
Was formed into a sheet (stock). Then, each original fabric was biaxially stretched by the following method to obtain a biaxially stretched film. The raw fabric was rolled at a rolling reduction of 0.5 and stretched twice in the machine direction, and then introduced into a tenter transverse stretching machine and then a roll longitudinal stretching machine to be biaxially stretched. At this time, the stretching ratio is 8 for transverse stretching.
And the longitudinal stretching were set to 3 times. The obtained biaxially stretched film has a stretching ratio of 6 times in the length and width with respect to the original fabric,
The thickness was 22 μm. The winding speed at this time is 5
It was m / min.

Table 1 shows the melting point, the stretching temperature, the stretching stability, and the tensile modulus of elasticity of the obtained film for each material. The stretching temperature indicated the optimum temperature range in the transverse stretching process for each composition. In the evaluation of the stretching stability, the one that could be stretched without being broken by continuous stretching for 1 hour was marked with ◯, the one that was from 30 minutes to 1 hour was marked with Δ, and the specimen with 30 minutes or less was marked with X.

The results in Table 1 show that the present invention lowered the stretching temperature and broadened the optimum stretching temperature range, and as a result, greatly improved the stretching stability. Further, the elastic modulus of the obtained film is also greatly improved depending on the composition as compared with the case of polyoxymethylene alone, which shows that the present invention also provides a stretched film which is more excellent in mechanical properties. .

[0027]

Example 2 and Comparative Example 2 Branched polyoxymethylene copolymer 10 obtained by copolymerizing the polyoxymethylene homopolymer of Example 1 with trioxane, ethylene oxide and 1,4-butanediol diglycidyl ether.
Polyoxymethylene and polyvinylphenol resin [Maruka Linker M-S2 manufactured by Maruzen Petrochemical Co., Ltd.] were mixed in the composition shown in Table 2 and molded into pellets in the same manner as in Example 1 below. After that, biaxial stretching was performed by the same method. The obtained film had a modulus of elasticity of 6 times both in the lengthwise direction and in the widthwise direction, and had a thickness of 22 μm.

Table 2 shows the melting point of each material,
The drawing temperature, the drawing stability and the tensile elastic modulus are described. The results in Table 2 also show the effects of the present invention in Table 1.

[0029]

Example 3 and Comparative Example 3 Polyoxymethylene homopolymer [Tenac # 3010 grade manufactured by Asahi Chemical Industry Co., Ltd.] and vinylphenol / styrene copolymer [vinylphenol / styrene = 70/30, Maruzen Petrochemical Co., Ltd.]
Maruka Linker CST70 grade] were mixed in the compositions shown in Table 3 to form pellets in the same manner as in Example 1, and then biaxially stretched by the same method. The obtained film has a modulus of elasticity of 6 times in both the length and width with respect to the original fabric,
The thickness was 22 μm.

Table 3 shows the melting points of the respective original fabrics,
The drawing temperature, the drawing stability and the tensile elastic modulus are described. The results in Table 3 also show the effects of the present invention in Table 1.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

INDUSTRIAL APPLICABILITY The biaxially stretched polyoxymethylene film of the present invention does not impair the excellent properties of polyoxymethylene and has excellent properties such as mechanical properties.
Further, the stretching performance and the stretching stability are greatly improved, which is extremely useful from an industrial viewpoint. The film of the present invention makes use of its excellent properties to make various applications such as a base film for a magnetic tape, a base film for a magnetic recording medium such as a floppy disk, or a base film for a heat-sensitive transfer sheet such as a ribbon cassette film for thermal transfer. It can be applied to fields.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29K 59:00 B29L 7:00 4F

Claims (1)

[Claims] 1. 50 to 99 parts by weight of a polyoxymethylene polymer in which the main part of the main chain is substantially composed of repeating units of an oxymethylene group — (CH ₂ —O) — and a polyvinylphenol resin or its derivative 50. To 1 part by weight of biaxially stretched polyoxymethylene film.