JP2514273B2 - Polymer melt molding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer melt-molding method, and more specifically, it suppresses adhesion of polymer deterioration products and a part of additives to the extruded surface of an extrusion die to obtain a high-quality molded product. The present invention relates to a polymer melt-molding method for stably molding a polymer.

[0002]

2. Description of the Related Art A die is used to melt and extrude a polymer. Conventionally, the material of the die is S45C, SS4.
Iron containing iron as the main component was used. However, corrosion occurs in the polymer flow path, which causes problems such as streak-like defects on the surface of the molded product. Therefore, the die is SUS420J2 or SUS630 which has an anticorrosive action.
Is implemented, and, for example, JP-A-63-1
In No. 83825, plating of Cr, Ni, etc., TiN, Si
It has been proposed to provide a rustproof coating with a sputtering film such as C.

However, in the case of extrusion molding using a die made of these materials, a molding defect called "eye stitch" often occurs. This is because polymer deterioration products, part of compounding agents, or their oxidation and decomposition products adhere to the extrusion surface of the die like "eye crocodile", and accumulate and stick to the extrusion surface (outer surface of the tip) of the die during molding. However, it is further deteriorated by heat, and this adhered material comes into contact with the molded product extruded from the die and causes a phenomenon that a convex scratch is formed on the surface of the molded product.

As a method for solving this problem, for example, Japanese Patent Laid-Open No. 63-153112 proposes that the surface layer portion of Cr plating covering the die is Cr ₂ O _3.
In general, it is difficult to obtain a satisfactory r ₂ O ₃ film only by changing the plating conditions.

Similarly, Japanese Patent Application Laid-Open No. 1-280525 proposes that the chemical composition of chromium in the surface layer is metal chromium ≤5 mol%, chromium oxide ≥50 mol%, and hydroxide + sulfate ≤33%. .

As a method for embodying this, 55 in air
There is a method of heat treatment at 0 ° C, but when heat treatment of chrome plating at such a high temperature, chrome plating generally causes stress cracking to generate microcracks, and surface hardness, which is an important characteristic of the die, is significantly reduced. There are problems and it is not practical.

As another means, Japanese Patent Laid-Open No. 63-293.
No. 032 discloses that the chromium composition ratio of the die is 12 to 100% by weight in the flow path of the polymer and 0 to 11% by weight on the lower surface of the die. Further, in JP-A-63-302016, the chromium composition ratio of the die is It is proposed that the polymer flow channel is 0 to 18% by weight and the lower surface of the die is 30 to 100% by weight. According to the additional test by the present inventor, no remarkable effect was found.

In general, the susceptibility to the occurrence of "eye bleeding" greatly varies depending on the heat resistance of the polymer, the melt viscosity, the compounding agent contained in the polymer, the filler, etc. even if the die is made of the same material. Therefore, when the "eye seal" grows and a defect is likely to occur in the molded product, the production of the molded product is interrupted and the "eye seal" is scraped off with a spatula of a soft metal such as copper. .

On the other hand, when the polymer passes through the inside of the die and is discharged into the air, the tip shape of the die has a great influence on the surface shape of the molded product. There is. JP-A-1-28191
In No. 6, the wetting angle between the polymer and the heated die is 70
Proposals have been made for spinnerets coated with ceramics that have a hardness of more than 0 ° C, but ceramics are generally high in hardness but poor in toughness and are liable to chip when impacted. When scratching the metal with a metal spatula, problems such as scratching and missing of the ceramic coating on the edge sometimes occur.

Further, Japanese Patent Laid-Open Nos. 1-281915 and 2-162010 propose a slit die made of a noble metal such as gold, platinum or tantalum, but the material is expensive and the hardness of the material is high. Is small, there is a problem that the base is easily scratched.

[0011]

The present inventor does not have a particularly difficult problem in implementing the present invention as in the above-mentioned prior art,
It is possible to significantly reduce the "eye dent" that adheres to the extrusion surface of the die,
Moreover, as a result of research on a method capable of molding a good product for a long period of time with almost no damage to the die even by a scraping operation of the "eye die" or the like, the present invention has been 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 channel of the molten polymer and / or the surface of the extrusion surface as the die has a wetting angle with triethylene glycol. Using a die composed of a hard sintered alloy composed of 30 to 95% by weight of a hard phase of an iron-containing complex boride and having a binder phase of 70 to 5% by weight of 40 ° or more. It is a method of melt-molding a characteristic polymer.

The polymer in the present invention is a thermoplastic polymer such as polyester such as polyethylene terephthalate, polyolefin such as polypropylene, vinyl polymer such as polyvinyl chloride, polyamide such as nylon 6 and polymethylmethacrylate. Examples include acrylic polymers. Of these, polyester is particularly preferable.

The die in the present invention is a die for spinning out fibers, an inflation die for extruding a film, a straight die, an extrusion die for wire coating, and the like.

The "wetting angle with triethylene glycol" in the present invention means a material, such as hard baking, which forms a surface on which droplets of reagent-grade triethylene glycol of a reagent grade come into contact with a molten polymer of a die under an atmosphere of 20 ° C. This is the contact angle created with the bond gold.

In the present invention, it is empirical fact of the present inventor that the surface characteristics of the material, especially the hard sintered alloy, are specified by triethylene glycol. The wetting angle with triethylene glycol has a higher correlation.

On the other hand, the wetting angle with the molten polymer is not suitable as a measure because of poor reproducibility of data due to the following reasons. That is, the melt viscosity of the thermoplastic polymer changes depending on the molecular weight of the polymer or the heating temperature. In addition, the molten polymer is decomposed by its heat or atmospheric gas,
It is difficult to obtain highly accurate and reproducible data because the crosslinking reaction may proceed in parallel. For the above reasons, triethylene glycol is convenient.

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

The complex boride containing iron that constitutes the hard phase of the hard sintered alloy is M _X N _Y B type (where M and N are metals,
X and Y represent the stoichiometric values necessary for M and N to form a compound), and M is Mo and / or W.
It is preferable that N is composed of one or more elements selected from Fe, Cr, and Ni, and the proportion of Fe in the hard phase is at least 10% by weight, preferably 10 to 22% by weight. The hard phase is an impurity element such as Al,
It may contain O or the like. The content of Mo and / or W is the atomic ratio of Mo and / or W (based on the atoms of boron).
It is preferably 0.75 to 1.25, and more preferably 0.90 to 1.20.

The above-mentioned compound borides are mainly Mo ₂ FeB ₂
Type, WFeB type or W ₂ FeB ₂ type complex boride, Mo and W may be mutually substituted, and Fe may be partially substituted by other elements such as Cr and Ni.

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

The hard sintered alloy is composed of the hard phase and the binder phase described above. For example, the B content is 3 to 8% by weight, the Cr content is 35% by weight or less, the Ni content is 35% by weight or less, and the Al content is 2%. 0.8 wt% or less, and Mo and / or W
The content is (Mo and / or W) / B at an atomic ratio of 0.7
It may be a sintered alloy having a range of 5 to 1.25 and the balance being Fe or an alloy of Fe and another element.

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

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

In the die of the present invention, the surface of the molten polymer channel and / or the extruded surface is made of a hard sintered alloy, and 30% or more of the surface, and further 4
It is preferable that 0% or more is occupied by the hard phase in the hard sintered alloy.

It is not clear why the die of the present invention is less likely to cause "eye bleeding". However, when a molten polymer is extruded using the die, the periphery of the polymer discharge port of the die is enlarged and observed. Although a very small eye die is often generated, this eye die substance stays in the die for a short time, and it is observed that the eye die material is taken off by the discharged polymer before the eye die grows largely. It is presumed that this detachment causes the stain on the die due to the eye blemishes to be 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.

At least a part of the surface of the die in the present invention is composed of a hard sintered alloy, and this structure includes a mode in which the surface of the base material is coated or laminated with a thin layer of the hard sintered alloy. . This base material may be one conventionally used as a die material, for example, carbon steel such as S45C and SS41, SUS420J.
2, it can be a non-rust steel such as SUS630.

[0028]

EXAMPLES The present invention will be further described below with reference to examples. Example 1 and Comparative Example 1 60% by weight of a hard phase of a complex boride containing Mo ₂ FeB ₂ as a main component and having an average particle size of 2 μm, and the balance of 70% by weight of Fe and C
The wetting angle of triethylene glycol was 60 °, which was made from a hard sintered alloy consisting of a binder phase containing 19% by weight of r and 9% by weight of Ni (relative to 100% by weight) as main constituents. The angle is 85
Use a mouthpiece with a slit width of 1.0 mm and a width of 38 mm.
The die was assembled into a 0 mm die, polyethylene terephthalate having a resin temperature of 285 ° C. was extruded, and a 100 μm-thick sheet was extruded onto a cooling roll at a speed of 30 m / min and taken out.

Almost no stripe-like defects due to eye crevices at the tip of the die were recognized even 72 hours after the start of extrusion.

On the other hand, as a result of extruding the sheet under the same conditions as in the above-mentioned example using a die of SUS420J2 as a die material, a streak-like defect due to eye blemishes was revealed within 36 hours from the start of extrusion.

[0031]

According to the present invention, the polymer flow passage surface and the polymer extruded surface of the die are made of a hard sintered alloy having low wettability, whereby "excessive die" is generated on the extruded surface of the die. Therefore, it is possible to stably form a high-quality extruded product having no stripe defects.

Claims (4)

(57) [Claims] 1. A method for extruding a molten polymer from a die, wherein the surface of the channel and / or the extrusion surface of the molten polymer as the die contains iron having a wetting angle with triethylene glycol of 40 ° or more. Boride hard phase 30-
70 to 5% by weight of a binder phase that binds 95% by weight and the hard phase
A method for melt-molding a polymer, which comprises using a die composed of a hard sintered alloy of 2. The hard-phase complex boride is of the M _X N _Y B type (where M and N are metals and X and Y are the stoichiometric amounts required to form compounds). Represents a numerical value), M is Mo and / or W, N is Fe, and Cr, N
The polymer melt-molding method according to claim 1, wherein the ratio of Fe contained in the hard phase is 10 to 22% by weight, which is composed of one or more elements selected from i. 3. The method of melt molding a polymer according to claim 1, wherein the crystal grain size of the hard phase is 0.1 to 100 μm. 4. The bonding phase is Fe or 1 of Fe and another element.
The method for melt-molding a polymer according to claim 1, wherein the polymer is an alloy composed of one or more kinds.