JPH04212827A - Melting molding method of polymer - Google Patents

Abstract

PURPOSE:To provide the melting molding method of a polymer preventing the generation of 'eye mucus' and stably molding a molded from having high quality though one parts, etc., of a polymer deteriorated substance and a compounding agent have adhered on the surface of a mouthpiece as 'eye mucus' and the surface characteristics of the molded form are deteriorated by 'eye mucus' when a molten polymer is extrusion-molded from the mouthpiece. CONSTITUTION:The melting molding method of a polymer is conducted in such a manner that the molten-polymer flow path of a mouthpiece and/or the surface of an extruding surface is composed of a hard sintered alloy consisting of 30-95wt.% hard phase of a double boride having the angle of wetting of 40 deg. or more with triethylene glycol and containing iron and 70-5wt.% bonding phase bonding said hard phase on extrusion molding.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for melt molding polymers, and more specifically, it suppresses the adhesion of polymer deterioration products and part of additives to the extrusion surface of an extrusion die, thereby producing high-quality molded products. This invention relates to a polymer melt molding method for stably molding a polymer.

0002

[Prior Art] A die is used to melt and extrude a polymer, and conventionally, the material of the die has been S45C, SS4, etc.
The main component used was first grade iron. However, corrosion occurs in the polymer flow path, which causes problems such as streak-like defects on the surface of the molded product. For this reason, it has not been implemented to construct the cap with rust-preventing SUS420J2 or SUS630. , for example, JP-A-63-18
In No. 3825, plating with Cr, Ni, etc., TiN, SiC
It has been proposed to apply a rust-preventive coating using a sputtered film such as .

However, when extrusion molding is performed using a die made of these materials, a molding defect called "eye stain" often occurs. This is because degraded polymers, part of the compounding agent, or their oxidized and decomposed products adhere to the extrusion surface of the die like "eye stain" and accumulate and stick to the extrusion surface (outer surface of the tip) of the die during molding. However, it further deteriorates due to heat, and this adhered material comes into contact with the molded product extruded from the die, causing a phenomenon in which convex scratches are created on the surface of the molded product.

As a method to solve this problem, for example, Japanese Patent Laid-Open No. 153112/1983 proposes that the surface layer of the Cr plating covering the cap be made of Cr2O3, but the Cr2O3 film is generally It is difficult to obtain a satisfactory film just by making changes.

Similarly, JP-A-1-280525 proposes that the chemical composition of surface chromium is metallic chromium≦5 mol%, chromium oxide≧50 mol%, and hydroxide+sulfate≦33%. .

[0006] As a method of realizing this, 55
There is a method of heat-treating chrome plating to 0℃, but if chrome plating is heat-treated at such high temperatures, chrome plating will generally cause stress cracks and microcracks, and the surface hardness, which is an important characteristic of the die, will decrease significantly. This poses challenges and is impractical.

[0007] As another means, Japanese Patent Application Laid-Open No. 63-293
No. 032 states that the chromium composition ratio of the mouthpiece is 12 to 100% by weight in the polymer flow path and 0 to 11% by weight on the bottom surface of the mouthpiece, and furthermore, in JP-A-63-302016, the chromium composition ratio of the mouthpiece is It is proposed that the content be 0 to 18% by weight in the polymer channel and 30 to 100% by weight on the bottom surface of the mouthpiece. According to the inventor's follow-up tests, no significant effects were found in any of them.

[0008] In general, the ease with which "eye stain" occurs varies greatly depending on the heat resistance, melt viscosity of the polymer, compounding agents contained in the polymer, fillers, etc., even if the caps are made of the same material. Therefore, when the "eye stain" grows and a defect appears on the molded product, it is necessary to stop the production of the molded product and scrape off the "eye stain" with a spatula made of a soft metal such as copper. .

On the other hand, the shape of the tip of the die when the polymer passes through the die and is discharged into the air has a large effect on the surface shape of the molded product, so it is generally finished to have an extremely sharp edge. There is. Japanese Patent Publication No. 1-28191
In No. 6, the wetting angle between the polymer and the heated cap is 70
Proposals have been made for caps coated with ceramics that have a hardness of at least 100°C, but ceramics generally have high hardness but poor toughness and are easily chipped when subjected to impact. When scratching with a metal spatula, problems such as scratching or chipping of the ceramic coating on the edge may occur.

[0010] Furthermore, slit dies made of precious metals such as gold, platinum, and tantalum have been proposed in JP-A-1-281915 and JP-A-2-162010, but the materials are expensive and the hardness of the materials is high. Since it is small, there are problems such as easy scratches on the cap.

[0011]

[Problems to be Solved by the Invention] The present inventor has found that there are no particularly difficult problems in implementing the invention as in the above-mentioned prior art;
The "eye stain" that adheres to the extrusion surface of the nozzle can be significantly reduced.
Moreover, as a result of research into a method that allows molding of a good product over a long period of time without causing any damage to the cap even when scraping off "eye stains" or the like, the present invention was achieved.

0012

[Means for Solving the Problems] That is, the present invention provides a method for extruding a molten polymer from a die, in which the flow path of the molten polymer and/or the surface of the extrusion surface as the die has a wetting angle with triethylene glycol. It is preferable to use a base made of a hard sintered alloy consisting of 30 to 95% by weight of a hard phase of a complex boride containing iron and 70 to 5% by weight of a binder phase that binds the hard phase, with an angle of 40° or more. This is a characteristic polymer melt molding method.

The polymer used in the present invention is a thermoplastic polymer, such as a polyester such as polyethylene terephthalate, a polyolefin such as polypropylene, a vinyl polymer such as polyvinyl chloride, a polyamide such as nylon 6, or a polymethyl methacrylate. Examples include acrylic polymers. Among these, polyester is particularly suitable.

The die used in the present invention refers to a die for spinning fibers, an inflation die or straight die for extrusion molding a film, an extrusion molding die used for coating electric wires, and the like.

In the present invention, the "wetting angle with triethylene glycol" refers to the material, such as a hard sintered material, that forms the surface on which droplets of reagent grade triethylene glycol come into contact with the molten polymer of the nozzle in an atmosphere of 20°C. This is the contact angle formed between the bond and the gold.

In the present invention, the reason why the surface characteristics of materials, especially hard sintered alloys, are specified using triethylene glycol is based on the experience of the present inventors. The reason is that the wetting angle with triethylene glycol has a higher correlation.

On the other hand, the wetting angle with the molten polymer has poor data reproducibility and is not suitable as a measure for the following reasons. That is, the melt viscosity of a thermoplastic polymer changes depending on the molecular weight or heating temperature of the polymer, and in addition, the molten polymer can be decomposed by heat or atmospheric gas, etc.
Crosslinking reactions, etc. may proceed in parallel, making it difficult to obtain accurate and reproducible data. For the above reasons, triethylene glycol is advantageous.

The hard sintered alloy in the present invention is a hard sintered alloy consisting of a hard phase of a complex boride containing iron and a binder phase that binds the hard phase, and the ratio of the hard phase to the binder phase is 30 to 9.
5% by weight to 70-5% by weight, preferably 40-90% by weight to 60-10% by weight.

The iron-containing complex boride constituting the hard phase of the hard sintered alloy is of the MX NY B type (where M and N are metals, and X and Y are the metals necessary for M and N to form a compound. (representing a stoichiometric value), M is Mo and/or W, and N is Fe, and 1 selected from Cr, Ni.
The proportion of Fe in the hard phase is at least 10% by weight, preferably 10 to 22% by weight.
It is preferable that The hard phase contains impurity elements such as Al
, O, etc. may be included. The content of Mo and/or W is preferably 0.75 to 1.25, more preferably 0.90 to 1.20 in terms of atomic ratio of Mo and/or W (to boron atoms).

[0020] The above-mentioned complex boride is mainly Mo2FeB
2 type, WFeB type, or W2 FeB2 type complex boride, Mo and W may be mutually substituted, and Fe may be partially substituted with other elements such as Cr and Ni.

[0021] The binder phase of the hard sintered alloy is Fe alone,
Alternatively, an alloy consisting of Fe and one or more other elements is preferable. Other elements include Cr, Ni,
Mo, W, Si, C, Co, Cu, Ti, V, Nb, T
Examples include a, Hf, Zr, P, and Al.

The hard sintered alloy consists of the above-mentioned hard phase and binder phase, and has, for example, a B content of 3 to 8% by weight, a Cr content of 35% by weight or less, a Ni content of 35% by weight or less, and an Al content of 2% by weight. .8% by weight or less, and Mo and/or W
Content is (Mo and/or W)/B atomic ratio 0.7
5 to 1.25, and the remainder may be a sintered alloy consisting of Fe or an alloy of Fe and other elements.

The crystal grain size of the hard phase in the hard sintered alloy is 0.
It is preferably 1 to 100 μm, more preferably 0.5 to 10 μm. Preferably, the crystal particles are uniformly dispersed in the binder phase.

Specific examples of such hard sintered alloys include, for example, Japanese Patent Publication No. 56-8904 and Japanese Patent Publication No. 56-157.
Publication No. 73, Special Publication No. 54-27818, Special Publication No. 6
Examples include those shown in Japanese Patent No. 0-57499 and the like. Among these, those having a "wetting angle with triethylene glycol" of 40° or more are used.

[0025] In the die according to the present invention, the surface of the molten polymer flow path and/or extrusion surface is composed of a hard sintered alloy, and 30% or more of the surface, more preferably 4
It is preferable that 0% or more is occupied by the hard phase in the hard sintered alloy.

[0026] The reason why "eye stain" is difficult to occur in the nozzle of the present invention is not clear, but when the molten polymer is extruded using the nozzle, an enlarged observation of the vicinity of the polymer discharge port of the nozzle shows that Very small eye stains often occur, but this eye stain substance stays in the mouth for a short time, and it is observed that the eye stain material is taken up by the discharged polymer and separated before it grows to a large size. It is presumed that due to this separation, the staining of the die due to eye stain becomes slight, and even if small convex scratches that do not substantially affect the surface quality of the molded product occur, large convex scratches do not occur.

The base of the present invention has at least a portion of its surface made of a hard sintered alloy, and this structure includes an aspect in which the surface of the base material is coated or laminated with a thin layer of the hard sintered alloy. . This base material can be a material conventionally used as a base material, such as carbon steel such as S45C or SS41, or SUS420J.
2. It can be made of rust-free steel such as SUS630.

[0028]

[Examples] The present invention will be further explained below with reference to Examples. Example 1 and Comparative Example 1 60% by weight of the hard phase of complex boride with an average particle size of 2 μm mainly composed of Mo2 FeB2, and the balance was 70% by weight Fe.
The wetting angle with triethylene glycol was 60° (note that the wetting angle of Teflon was Wetting angle is 8
Using a 5°) nozzle, assemble this into a die with a slit width of 1.0 mm and a width of 380 mm, extrude polyethylene terephthalate at a resin temperature of 285°C, and extrude a 100 μm thick sheet onto a cooling roll at a speed of 30 m/min. I took it away.

[0029] Barely any streak-like defects caused by eye stain at the tip of the die were observed even 72 hours after the start of extrusion.

On the other hand, when a sheet was extruded using a die made of SUS420J2 under the same conditions as in the above example, a streak-like defect caused by eye stain became apparent 36 hours after the start of extrusion.

[0031]

[Effects of the Invention] According to the present invention, the polymer flow path surface and the polymer extrusion surface of the die are made of a hard sintered alloy with low wettability, which prevents the occurrence of "eye stain" on the extrusion surface of the die. This makes it possible to stably mold high-quality extruded products without streak-like defects.

Claims (4)

[Claims] 1. A method of extrusion molding a molten polymer from a die, in which the die is made of iron-containing composite material having a wetting angle with triethylene glycol of 40° or more and a flow path for the molten polymer and/or an extrusion surface. Boride hard phase 30~
95% by weight and 70-5% by weight of a binder phase that binds the hard phase.
1. A polymer melt-molding method characterized by using a die made of a hard sintered alloy. [Claim 2] The hard phase complex boride is MX NY B type (
Here, M and N are metals, and X and Y represent the stoichiometric values necessary for M and N to form a compound.
M is Mo and/or W, N is Fe, and Cr
, Ni, and the proportion of Fe in the hard phase is 10 to 22% by weight. 3. The method for melt molding a polymer according to claim 1 or 2, wherein the hard phase has a crystal grain size of 0.1 to 100 μm. Claim 4: The binder phase is Fe, or one of Fe and other elements.
The method for melt-molding a polymer according to claim 1, wherein the polymer is an alloy consisting of at least one species.