JPH01280525A - Molding mouth piece - Google Patents

Abstract

PURPOSE:To constitute the title mouth piece so that a linear defect does not appear on the surface of a film to be molded, by a method wherein a surface part where a molten polymer is fluidized and stuck and the polymer are peeled off from a slit of the mouth piece and a chemical composition of chrome of the surface layer of a molding mouth piece obtained by performing chrome plating of the surface part where it begins to come into contact with air is specified. CONSTITUTION:In the case where a mouth piece material for molding is chrome plated, in many cases oxidative decomposition/gelation are apt to progress in a considerable short period of time as compared with a molded mouth piece consisting mainly of ordinary iron. The above matter is conspicuous in the case where the same is in an intimate mutual relation with a chrome plated surface, especially a chemical composition of chrome of an extreme surface layer part up to 100Angstrom , a large quantities of chrome hydroxide or sulfate out of the extreme surface layer chrome are contained, and only a small quantity of chrome oxide is contained. In other words, it is necessary to satisfy relative formulas of metallic chrome <=5%, chrome oxide >=50mol%, hydroxide + sulfide <=33mol% to cause a polymer not to gel in a short period of time.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a molding die.

As a die for polymer molding, 545 whose main component is iron is used.
CD, 330G, and even 5KD alloyed with a small amount of chromium.
61 and 5KD11 are used.

[Problems to be Solved by the Invention] However, the above-mentioned conventional molding die has the following problems.

(1) Because iron is the main component, rust occurs easily, and as a result, the polymer flow that passes through the rusted area is disturbed.
This causes streak-like surface defects and uneven sheet thickness on the polymer surface that exits the die.

(2) On the other hand, when chromium is alloyed to prevent rust, the iron material becomes hard and has poor polishability and openability. In order to eliminate this defect, it is necessary to mix a large amount of sulfur and lead, but this will make it easier for rust to progress due to stress crack corrosion near the sulfur and lead, which will eventually lead to surface defects of the film. Become.

(3) There have also been attempts to improve corrosion and wear resistance by applying chrome plating to the surface of iron, but chrome plating is prone to cracks and cracks, especially on the end faces, resulting in so-called " This tends to result in a "blooming" state, which not only results in insufficient corrosion protection, but also causes heavy metals and compounds such as antimony and germanium to adhere to these cracks, causing surface defects on the film.

(4) Furthermore, in the case of chrome-plated caps, oxidative deterioration and gelation of the polymer may occur at the tip of the cap lip, resulting in deposits on the cap lip called "eye mucus". This may appear as streak-like defects on the surface of the film being molded.

An object of the present invention is to provide a molding die that has improved the above-mentioned problems.

[Means for Solving the Problems] The present invention provides a molding die in which the surface portion to which a molten polymer flows and adheres and the surface portion where the polymer peels off from the die slit and comes into contact with air are plated with chrome. The present invention relates to a molding die characterized in that the chemical composition of chromium in the surface layer of the chromium-plated portion satisfies the following formula.

Metallic chromium 55 mol% Oxide 206250 mol% Hydroxide Dry sulfate ≦33 mol% Next, the molding die as used in the present invention is a polymer melt or solution with an undefined shape that can be formed from a slit that can be molded into a sheet shape. Refers to the device configured. Examples of typical molding dies are detailed in Japanese Patent Publication No. 50-1894, etc., but the conceptual classification of dies include straight dies, which are represented by tube dies, and inflation dies. There are dies such as cross radial dies such as , offset dies, fishtil dies, manifold dies, and coat hanger dies. Further details are described in Keiji Sawada's ``Plastic Extrusion Molding and Its Applications'' (published by Seibundo Shinkosha).

Preferred polymers suitable for the cap according to the present invention include linear thermoplastic polymers that increase fluidity when heated, particularly polyesters, polyphenylene sulfides, and the like.

Polyester in the present invention refers to polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, polyethylene bisphenoxycarboxylate, or modified products thereof. In addition, polyphenylene sulfide is a compound having a main chain in which two Fe groups are bonded with sulfur, and may contain ether, sulfone, ketone, meta bonding group, etc. as a copolymer component. This is described in Japanese Patent Publication No. 59-5100.

Chrome plating is the process of plating chromium onto metals mainly made of iron, copper, aluminum, etc. using a plating solution containing chromic acid and a small amount of sulfuric acid using direct current. The thickness of the chromium plating at this time can be freely changed depending on the application, but a thickness of about 100 to 500 μm is generally widely used. Of course, to prevent defects such as cracks, cracks, chips, etc. from occurring on the chrome plated surface, we optimize the plating conditions, add additives, increase the cleanliness of the plating surface, and optimize the surface roughness. After plating with other elements, such as nickel, before chromium plating and performing a so-called base treatment, the second step is
Three-stage and multi-stage plating may be performed.

Chrome-plated materials are generally considered to be chemically stable. However, when chrome plating is used for the molding die, it is not necessarily more stable than ordinary iron-based materials. In other words, in the case of chrome plating, the polymer that adheres to the lower surface of the lip, which is exposed to the atmosphere rather than the path of the polymer melt, at the tip of the mouthpiece lip, is chrome plated when the molding mouthpiece material is chrome plated.
In many cases, oxidative decomposition and gelation progress easily in a considerably shorter time than with ordinary molded die made mainly of iron.

This is closely correlated with the chemical composition of chromium on the surface of chrome plating, especially in the outermost layer of up to 100 layers.The outermost layer of chromium contains a large amount of chromium hydroxide and sulfate, and a small amount of chromium oxide. This is noticeable when only the That is, in order to prevent the polymer from gelling in a short time, it is necessary to satisfy the following relational expression: 55 mol% of metallic chromium, 206,250 mol% of oxidation, hydroxide±faM salt≦33 mol%.

The amount of metallic chromium Cr is 5 mol% or less, preferably 0%. Since chromium metal has a large ionization tendency, it easily undergoes ion exchange with other metals, and as a result, it easily forms compounds with other negative ions, and as a result, it tends to cause surface defects on extruded films. Therefore, metallic chromium C
r is preferably 5% or less, preferably 0%. There are various methods to reduce the content of metallic chromium Cr, but the most efficient method is preferably to heat the sample at 550° C. or higher for 2 hours or more.

(hydroxide child sulfate) is 33 mol% or less, preferably 2
It is 5 mol% or less. This means that hydroxides and sulfates are
Dehydration reaction occurs easily by heating to around 300℃,
This water hydrolyzes polymers such as polyester,
This is because the air in the atmosphere induces gelation of the polymer. Therefore, it is most preferable that it contains no sulfate or chromium hydroxide (compounds that are easily dehydrated such as Cr00H and Cr(OH)3). This is because if a gelled three-dimensional polymer is formed and adhered to the lower surface of the mouth lip, it will cause convex or concave streak-like defects on the surface of the extruded polymer film. this(
In order to reduce the content of hydroxide + 5A acid salts, the bath temperature for chromium plating should be set at a low temperature of 20 to 60°C, or the temperature should be lowered to 350°C or higher in air or vacuum, more preferably 550°C.
A method such as heat treatment at ℃ or higher for 1 hour or more is effective.

Chromium oxide CrOχ is 50 mol% or more, preferably 6
The content should be 0 mol% or more, more preferably 70 mol% or more.

Chromium element is relatively active, but chromium oxide,
In particular, chromium trioxide is a fairly stable compound, and unless this compound is the main component, stable chemical inertness cannot be obtained.

This is because even though chromium oxide is the same, as it becomes tetravalent, pentavalent, and even hexavalent chromium, it tends to react with other things and becomes a more or less unstable compound.

That is, compared to 3(i[j), 4-valent, 5-valent, 6-valent
When using high-value and expensive compounds, the polymer tends to undergo oxidative decomposition and gelation within a relatively short period of time. In other words, if the chrome plating surface is coated with trivalent chromium oxide, there is no practical problem, but if it is coated with a layer containing tetravalent, pentavalent, or hexavalent chromium oxide, the base Polymer gelation is relatively likely to occur at the tip of the lip, and as a result, streak-like (convex) surface defects are likely to occur on the surface of the formed sheet. In this way, even with the same chrome plating, it becomes mainly trivalent Cr2O3 or trivalent Cr (
OH)3 or Cr0OH16-valent CrO:+ is determined.

The content of hexavalent chromium oxide CrO3 is preferably 20 mol% or less, more preferably 10 mol% or less.

In the case of a plating cap, the sharpness R of the tip of the polymer discharge lip is preferably 100 μm or less, more preferably 30 μm or less.
It is desirable that the thickness be less than .mu.m so that the peelability is uniform, that is, the surface does not become rough in the width direction.

In order to create a cap with a sharp tip like this, the so-called "metsuki-shun" polishing is prone to cracks during polishing, so before plating, an auxiliary jig was applied to the tip of the cap lip with a gap of 100 to 500 μm. Post-plating can prevent cracks from forming in some corners and from cracking during polishing.

The material to be plated is not particularly limited, but it is a metal mainly composed of iron, containing as little sulfur, phosphorus, carbon, and manganese as possible.
Moreover, a material containing a large amount of nickel, chromium, etc. is preferable.

The hardness of the cap should be 28 to 45 degrees in HRC hardness, preferably 31 to 45 degrees, taking into account polishability, workability, handling, etc.
A range of 40 degrees is good.

The shape of the molding die is not particularly limited, but it can be applied to any shape such as a circular die, T die, or L die.

In addition, when the molding die of the present invention uses polyester as the polymer, the elution of iron ions (hereinafter referred to as rust prevention rate) when immersed in an ethylene glycol solution of an antimony compound is preferably 20 ppm or less, more preferably It is preferable to use a material whose main component is iron, which is 110C1 or less.

If a material with a rust prevention rate exceeding 20 C)m is used, as iron ions are eluted from the surface of the molding die, antimony metal, which is the reduced form of an antimony compound, will be unevenly distributed and precipitated in areas where iron ions are easily eluted. .

As a result, convex projections are generated on the surface of the die, which causes concave streak-like defects on the surface of the discharged polymer film. If the size of the irregularly deposited convex projections on the die surface is 5 to 10 μm or more, concave streak-like defects will appear on the discharged film surface. The size of this cap surface defect is 1. Even a small one is 5 to 10 μm, and a large one is about 10 mm.

[Measurement method] (1) The hardness of the cap is expressed as Rockwell hardness measured on the C scale according to JIS Z2245 (HRC).
.

(2) The chemical composition of chromium in the extreme surface layer of chromium plating was determined using X-ray photoelectron spectroscopy (XPS method) as follows. In the XPS method, a sample surface placed in an ultra-high vacuum is irradiated with monochromatic soft X-rays, and photoelectrons emitted from the surface (~several 10 people) are divided in energy and detected by an analyzer. The binding energy of bound electrons in a substance is obtained as a spectrum, information on surface elements is obtained from the energy values of atomic orbitals, and information on valence and bonding state is obtained from the energy shift of each peak.

The device is “ESCA” manufactured by VG 5 scientific.
LAB5J was used. The analysis conditions are as follows.

・X-ray source MQKα1,2 -X-ray output 10kv 20mA ・Anizer mode Con5tant Analtser Energy
(CAE) ) (odePass t:neray -
------WIDE 5CAN 50eVNARRO
W 5CAN 20eV ・Resolution Ag5d5/2FWHH=1. OeV・Vacuum degree 2×10−9 mb・Temperature 20°C・Sampling Fixed to the sample stand with graphite paste.

・Horizontal axis correction 01. of neutral carbon. Peak value 284.6e
I made it to V.

・Data processing Smoothing satellite 5ubtractionpeak
5ynthesis The distance between the metal components in the difference spectrum is determined from the difference spectrum obtained by subtracting the spectrum of metallic chromium from the total spectrum. The bonding state of chromium and oxygen was determined by the peak splitting method and divided into those that exist as oxides (I), those that exist as hydroxides and sulfates (n), and those that are none of the above (If). , each expressed as a percentage of total oxygen. Of course, if A% of metallic chromium is included, (
It is expressed as the ratio of the bonded state of oxygen in 1-A)%.

(3) Rust prevention rate An ethylene glycol solution of an antimony compound is prepared by adding 2% antimony trioxide to ethylene glycol.
Use a solution that has been completely dissolved in a glass container at 10°C.

The conditions for immersing the test piece were as follows: A test piece with a specific surface area of 150 cm2 was completely immersed in a glass container containing the ethylene glycol solution of the antimony compound at 25°C and 10°C, and a reflux condenser was attached. ℃
After treatment for 4 hours, the test piece was immediately taken out to room temperature.

Of course, in the case of a coated sample, the entire surface must be coated because it will be immersed in a liquid.

On the other hand, if only the inside of the cap is coated, with the cap still assembled, line the cap slit with silicone resin that hardens at room temperature to prevent the liquid from flowing out, and then stand the cap with the slit at the bottom. Attach a reflux condenser to the place where the upper polymer enters, inject the nyletine glycol solution of the above antimony compound, make sure that the entire mouth surface is immersed in the liquid, and heat it to 170°C with a mouth heater for 4 hours. do. Immediately unclog the bottom surface with silicone resin and transfer the processing solution to another glass container.

The eluted iron ion sample is corrected to match 150 Cm2/D.

The determination of iron ions in the obtained treatment solution is as follows.

1) Precisely weigh 1 g of the scanning sample into a beaker (100 mD), add 5 rrl of sulfuric acid, and heat on a heater (approximately 300° C.) to carbonize the sample. Gradually add nitric acid and heat to decompose. When the sample becomes colorless or transparent, heat it until just before drying and concentrate. After cooling, add 10 mff of acid and heat (approximately 200℃
) and dissolve.

After cooling to room temperature, transfer to a 25m0 volumetric flask with ion-exchanged distilled water and dilute to the marked line.

A blank test was conducted in the same manner as above, and the obtained solution was sprayed into argon plasma, and inductively coupled high frequency plasma generation spectrometry (Inductively Coupled Plasma generation spectrometry) was conducted.
sma Atomic Emission Spect
iron (measured wavelength is 259.94n
m> is measured.

Determine the amount of iron from the calibration curve created in advance. Calculate the iron content in the sample using the following formula.

Iron (μg/a) = (S-3b) xV/WS: Iron concentration (μ
g/mD,) Sb: Iron concentration corresponding to the luminescence intensity of the blank test solution prepared from the calibration curve (μg/mj2) ■=Measurement solution volume (mQ> W: Sampling test) (g) ii) Calibration curve creation Manipulation iron standard stock solution (1,0mQFe/mQ> met(1+4
> to prepare an iron standard solution in the range of o to 2o (μgFe/mα).

Measure the iron standard solution in the same way as the sample, and create a relationship line between iron concentration and luminescence intensity.

i) Apparatus A sequential ICP emission spectrometer 5PS1100 manufactured by Seiko Electronics Industries was used.

[Effects of the invention] By specifying the chemical composition of chromium on the surface in contact with the molten polymer in a chrome-plated mouthpiece, surface defects such as convex or concave streaks on the surface of the film to be formed can be prevented over a long period of time. A film with a smooth and uniform surface is obtained without any appearance of film.

[Example] The present invention will be explained based on examples.

Example 1 As shown in the table, 5KD-61 was used as the base material for the base material.
A cap with two-step chrome plating (thickness 200 μm) was used on the portion corresponding to the polymer flow path. The base is
Slit width 2mm, width 1900mm, base material 5KD-61
A T-die cap with HRC hardness of 40 degrees is used, and this is 250 m
Attach it to the tip of an extruder (m), uniformly heat the nozzle temperature to 285°C, and add polyethylene terephthalate (intrinsic viscosity [η] in 0-chlorphenol = 0.6) to the extruder.
2dff/q, using antimony trioxide as a polymerization catalyst)
was heated and welded to 285° C., the melt was extruded from the above-mentioned die, and cooled with a cast drum while applying an electrostatic charge in a conventional manner to obtain a cast sheet with a thickness of 180 μm.

The cast sheet was stretched under known biaxial stretching conditions, that is, stretched 6 times in the longitudinal direction with a multi-stage opening, and stretched 4° and 5 times in the width direction.
This was heat-treated at 200°C to obtain a film with a thickness of 7 μm.

The chemical composition of the surface chromium plating thus obtained was 0 mol% of metallic chromium, 72% of chromium trioxide Cr2o3,
It contained 28 mol% of chromium hydroxide and sulfate.

Even after continuous film formation for one week using the die, no streak-like surface defects were observed.

Example 2, Comparative Examples 1 to 3 Using the same shape and material as the cap used in Example 1, the heat treatment conditions after chrome plating were changed, and the thickness was 7 μm in the same manner as in Example. A biaxially stretched film was obtained.

The cast sheets thus obtained were classified into the following categories based on the time at which surface defects appeared.

As shown in Table 1, the heat treatment temperature in air was 550℃.
It can be seen that by increasing the chemical composition to a higher value, the chemical composition falls within the claims of the present invention, and as a result, a film with no surface defects can be obtained stably for a long period of time.

Table 1 Procedural amendment [ 1985 Patent Application No. 218350M 2. Invention 0 Title 1 Molding base 3, LEft61 1 Relationship to case Patent applicant address 2-2-1-5, Nihonbashi Muromachi, Chuo-ku, Tokyo, by amendment Increasing number of inventions None 6, subject of amendment
1. In the "Claims" and "Detailed Description of the Invention" columns of the specification (1) The claims are amended as shown in the attached sheet.

(2) 4th line from the bottom of page 1 - Correct 345CDJ to rs45cJ.

(3) Page 3, line 10 Correct "one adhesion" to "contact".

(4) Page 10, line 13 Correct "with hardness" as "with hardness".

(5) 4th line from the bottom of No. 10 Correct “Kotoka” to “Koto”.

(6) Page 11, line 4 Correct r20pmJ to r20ppmJ.

(7) Page 11, line 10 Correct "mouth anomaly" to "uneven distribution".

(8) Page 11, line 12 Correct "washed" to "appear".

Attached Patent Claims A molding die in which a surface portion with which a molten polymer comes into fluid contact and a surface portion where the polymer peels off from a die slit and comes into contact with air are chromium-plated, wherein the surface layer of the chromium-plated portion is A molding die characterized in that the chemical composition of chromium satisfies the following formula.

Metallic chromium 65 mol% Chromium oxide 250 mol% Hydroxide + sulfate ≦33 mol%

Claims (1)

[Claims] In a molding die in which the surface portion to which a molten polymer flows and adheres and the surface portion where the polymer peels off from the die slit and comes into contact with air are chrome plated, the surface layer of the chromium-plated portion A molding die characterized in that the chemical composition of chromium satisfies the following formula. Metallic chromium ≦5 mol% Chromium oxide ≧50 mol% Hydroxide + sulfate ≦33 mol%