JP2947877B2 - Release film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to various structural parts of an aircraft, such as a vertical tail of an aircraft, a wheel accommodating door, a radar accommodating body, and a baffle for braking, and a structure of an automobile or a hull. When molding composite materials that require heat resistance, such as parts or printed circuit boards, it is used to release the mold from the molded product.
The present invention relates to a release film containing a fluoropolymer.

[Prior Art] As a release film as described above, a film disclosed in
There was one disclosed in JP-A-52-58870.

According to this conventional example, when laminating a thermosetting resin prepreg requiring high-temperature molding, a fluorinated polyethylene having a low degree of fluorination obtained by a casting method is used as a release film (sheet) on the surface of the laminated prepreg. ing.

By the way, the reinforcing fibers used for the composite material are carbon fibers and aramid fibers, and the composite material itself is colored black or yellow. It is very important to check whether a release film has been loaded during processing of such a composite material, and if the release film has been damaged during processing, whether it has adhered to the molded composite material. is important. If the process proceeds to the next step while the damaged film remains attached to the composite material, a fatal defect will be caused by bonding or the like.

From such a background, the color of the release film is most preferably red.

Although the coloring function of the release film is contradictory, it is preferable that both the hiding power (the degree of coloring) and the transparency are compatible.

Transparency is necessary to be able to recognize the various materials below through the release film, for example, to know what the material is or to read a character mark written on the composite material.

In order to obtain such a release film and to require heat resistance, conventionally, as pigments for coloring red, cadmium sulfide CdS and cadmium selenide CdSe have been used.
Cadmium red whose main component is used.

[Problems to be Solved by the Invention] However, although the above-mentioned cadmium red is excellent in heat resistance and also in coloring and hiding power, it is highly toxic and harmful, and its use is restricted.

On the other hand, fluororesin is thermally decomposed during melt extrusion. There is a problem that decomposition products containing fluorine and hydrogen fluoride produced by the reaction of the decomposition products with water corrode and damage the extrusion equipment.

Although conventional pigments such as cadmium red have a coloring function, such a thermal decomposition behavior of a fluororesin cannot be suppressed by blending the pigment.

The present invention has been made in view of such circumstances, and aims to provide a harmless release film while having excellent heat resistance, coloring power, and hiding power, and also has an advantage in extrusion processing. An object of the present invention is to suppress corrosion of equipment due to thermal decomposition of a fluororesin.

[Means for Solving the Problems] The release film according to the present invention contains a fluorine-containing polymer and 85% by weight or more of ferric oxide in order to achieve such an object. Average particle size 0.05-10μ
m, and a concentration of the red pigment with respect to the fluoropolymer is 0.1 to 2.0% by weight.

With a fluoropolymer, Wherein R ₁ is F, —R _f , or —O—R _f , and R _f is a perfluoroalkyl group having 1 to 12 carbon atoms. This includes a polymer having such a component and copolymerized with another ethylenically unsaturated monomer such as ethylene.

As the fluorine-containing polymer used in the present invention, the following ethylene tetrafluoride copolymer is preferable from the viewpoint of mold release properties and heat resistance.

Copolymer of ethylene tetrafluoride and hexapropylene Specific examples of this copolymer include ethylene tetrafluoride 95
Some have a composition of about 50% by weight and about 5% by weight of hexafluoropropylene.

Copolymer of ethylene tetrafluoride and perfluoroalkyl vinyl ether Specific examples of this copolymer include ethylene tetrafluoride 95
Some compositions have a composition of about 50% by weight and about 50% by weight of perfluoropropyl vinyl ether.

Copolymer of ethylene tetrafluoride and ethylene Copolymer of chlorotrifluoroethylene and ethylene In addition, as a fluorine-containing polymer, from the kneading property with ferric oxide, thermoplasticity, and fluidity under heating It is preferable to use one having excellent properties.

The melt viscosity of the copolymer, it is desirable melt viscosity at a temperature of melting point + 60 ℃ is 10 ⁶ poises. It is better not to use polytetrafluoroethylene because it exceeds the above viscosity.

For high temperature processing conditions, ethylene tetrafluoride, hexafluoropropylene copolymer and ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer are suitable.

The red pigment containing ferric oxide contains ferric oxide (Fe ₂ O ₃ ) as a main component.

The red pigment is produced by a dry method or a wet method using ferrous sulfate, iron chloride or the like as a raw material.

In the dry method, ferrous sulfate is pyrolyzed by firing to produce ferric oxide. The desired composition is obtained by adjusting the firing temperature and time.

In the wet method, caustic soda, soda ash, ammonia or the like is added to a ferrous sulfate solution to make ferrous hydroxide, and then oxidized by blowing air or the like to obtain a precipitate of ferric hydroxide. The precipitate of ferric hydroxide is separated by filtration, dried and baking to obtain ferric oxide.

As another wet method, iron is put into a ferrous sulfate solution,
There is a method in which air is blown while heating to carry out hydrolysis. In this reaction, sulfuric acid is produced, but immediately reacts with iron to make the composition of the solution ferrous sulfate, and subsequent hydrolysis yields a precipitate of ferric hydroxide. The precipitate of ferric hydroxide is separated by filtration, dried and baking to obtain ferric oxide.

In addition to ferric oxide, the components contained in the red pigment include raw materials or intermediate residues in the production process, and ferric oxide.
Fe ₃ O ₄ or calcium sulfate CaSO ₄ or _{SiO 2, Al 2 O 3,} CaO, Mg
There are oxides such as O.

Raw materials or intermediate residues in the production process include ferrous sulfate such as ferrous sulfate FeSO ₄ and ferric sulfate Fe ₂ (SO ₄ ) ₃ , and ferrous hydroxide Fe (OH) ₂ and ferric hydroxide Iron Fe ₂ O ₃ xH ₂
There is iron hydroxide such as O or FeO (OH).

The content of ferric oxide is 85% by weight or more. 85% by weight
If it is less than this, a red color suitable for identification cannot be obtained.
In addition, the effect of suppressing the thermal decomposition of the fluororesin becomes insufficient. It is preferably at least 93% by weight.

Further, even if the content of ferric oxide is reduced to less than 85% by weight and the residue is supplemented with a compound similar to ferric oxide, a red color suitable for identification cannot be obtained.

For example, when the composition of the red pigment contains 15% by weight or more of triiron tetroxide, it becomes black and the discrimination function is reduced. Further, when 15% by weight or more of ferric hydroxide is contained, the color is yellowish and the discrimination function is similarly reduced.

Other expressions of ferric oxide include iron (III) oxide, diiron trioxide, and ferric oxide.

In addition, red pigments containing ferric oxide as a main component include red pigments such as red iron oxide, red iron oxide, red iron oxide, red iron oxide, and the like. It can be used as a coloring agent of the invention.

The ferric oxide crystal includes a hexagonal crystal, a spinel crystal, and an orthorhombic crystal.

The average value and distribution of the particle size of ferric oxide are important in terms of the hiding power, see-through properties, dispersibility in resin, and the filter life of the filter used in the step of extruding the film, for the colored release film. . As described above, in the release film, it is preferable that both the hiding power (degree of coloring) and the transparency are compatible. For this reason, it is preferable that the particle size distribution is narrower while having a specified value of the particle size. preferable.

The average particle size of the ferric oxide is 0.05 to 10 μm, preferably 0.1 to 1 μm. If the thickness is less than 0.05 μm, the concealing power decreases and it is difficult to identify the release film. On the other hand, if the thickness exceeds 10 μm, the transparency decreases or the filter in the extrusion process is clogged, thereby shortening the filtration life of the filter. This causes a problem that causes

When dispersing a red pigment containing ferric oxide as a main component in the fluoropolymer, it is necessary to uniformly disperse and prevent secondary aggregation of particles in the processing step, using a dispersant, Prevent secondary aggregation and increase the uniformity of dispersion.

As the dispersant, a surfactant is generally used,
In the case of a release film, if the dispersant is transferred to the composite material to be processed, it will hinder subsequent surface processing. In particular, transfer contamination is more likely to occur in a release film used under high temperature conditions. In order to avoid such a problem, the following method is used.

A mixture is prepared by uniformly mixing a red pigment containing ferric oxide as a main component and a fine powdery fluoropolymer, and the mixture is extruded and kneaded with the fluoropolymer. The particle size of the finely powdered fluoropolymer is preferably 1 μm or less, and includes a dry powder and a liquid dispersion.

As a powdery fluoropolymer, for example, 0.2 to 0.3
Good results are obtained with a particle size of μm. The finely powdered fluorine-containing polymer may be the same as the fluorine-containing polymer which is the main component of the final blend, but may have the same chemical composition and a small molecular weight, or adjust the copolymer composition and copolymer components. It is preferable to use one having a lower melting point.

Ferric oxide includes transparent iron oxide pigments and transparent red iron oxide, which have an average particle size of 0.01 to 0.05.
Since it is as thin as μm, the hiding power is limited, and the color tends to fluctuate and the discrimination function is inferior.

Next, an example of a preferred production method of the release film will be described.

A red pigment containing at least 85% by weight of ferric oxide and a finely powdered fluoropolymer are mixed by a screw kneader or a rotor kneader.

The obtained kneaded product and the fluoropolymer are kneaded and extruded using a screw type extruder to prepare a master pellet.
A twin screw extruder is preferred for uniform kneading.

The content of the red pigment in the master pellet is preferably from 10 to 20% by weight.

Without going through the above-mentioned step, the red pigment and the fluoropolymer may be kneaded and extruded by a screw type extruder to produce master pellets. At this time, the fluoropolymer is preferably in the form of fine particles or flakes.

The master pellet and the fluorinated polymer are mixed so that the concentration of the red pigment with respect to the fluorinated polymer becomes a predetermined value, and the mixture is used as an extrusion raw material.

The concentration of the red pigment with respect to the fluoropolymer is 0.1 to 2.0% by weight based on the balance between hiding power and transparency. 0.1% by weight
If it is less than 2.0%, the discrimination function is deteriorated, and if it exceeds 2.0% by weight, the fluoroscopic function is lost.

[Action] According to the release film of the present invention, the identification function is provided by the red pigment while maintaining the release function obtained by the heat resistance, low surface energy and chemical resistance of the fluoropolymer. Can be.

That is, for example, in the case of a tetrafluoroethylene / hexafluoropropylene copolymer film or a tetrafluoroethylene / perfluoropropylvinyl ether copolymer film, the light transmittance is 96% at a thickness of 100 μm or less. , Cloudiness
The transparency is remarkably excellent, as in the case of 0.2 to 0.5%, and it is difficult to identify the presence by handling during processing. This can be avoided by coloring red with a red pigment.

Fluoropolymers are polymers with a high degree of polymerization, and are often extruded at a temperature above the melting point + 50 ° C. With heating at high temperatures, the fluoropolymers are thermally decomposed and low molecular compounds containing fluorine. Is released, and by the released fluorine and hydrogen fluoride generated by reacting with the moisture in the air,
There was a problem that the extruder and peripheral equipment were corroded, but according to the release film of the present invention, such corrosion can be suppressed. The mechanism has not been elucidated yet, but it is speculated that it may be due to suppression of thermal decomposition itself, adsorption of decomposition products, and capture of decomposition products by some chemical reaction.

The release film can be made harmless by the red pigment containing ferric oxide as a main component.

A red pigment containing ferric oxide as a main component can exert a hiding power with a small amount.

[Example] Hereinafter, an example of the present invention will be described in detail.

As a red pigment, Bengala pigment, EP-OOD manufactured by Nippon Bengaro Kogyo KK was used. This red pigment contains 98% by weight of ferric oxide and has an average particle size of 0.2 μm. 60 parts by weight of this red pigment were mixed with 40 parts by weight of an ethylene tetrafluoride / propylene hexafluoride copolymer (copolymer composition: 87% by weight, 13% by weight) (average particle size: 0.5 μm), and a Banbury type mixer was used. And kneaded.

25 parts by weight of this compound were mixed with a tetrafluoroethylene / hexafluoropropylene copolymer (manufactured by DuPont-Mitsui Fluorochemicals,
75 parts by weight of “Teflon” FEP100J) pellets were blended to prepare a master pellet at an extrusion temperature of 350 ° C. using a screw-type twin-screw extruder.

1 part by weight of master pellet "Teflon" FEP100 J42
Extrusion temperature of 5 tons was obtained by blending parts by weight. Using a film forming machine equipped with a T-type die on a screw type single screw extruder, the extrusion temperature was adjusted.
At 355 ° C., a 25 μm thick film was processed and created. The concentration of the red pigment with respect to the fluoropolymer is 0.35% by weight.

The resulting film exhibited a reddish-brown color, a color suitable for discrimination, and the color was uniform. In addition, it was transparent, and it was possible to observe the condition of the object below and touch the mark.

When the parallel light transmittance and the haze value of the obtained film were measured according to JISK6714, they were 75% and 23%.

After the end of the film forming process, the extrusion system was dismantled and washed,
No significant corrosion progress was observed.

The extrusion system used a Ni-based corrosion-resistant alloy and the filter element was made of SUS304, but there was no particular problem.

Without blending the red pigment used in the present invention, when extruding a single composition of “Teflon” FEP100J for 5 tons, the filter element made of SUS304 is corroded in the latter half of processing,
A part of the film was peeled off and dropped, and was mixed as a foreign substance in the film.

The film of this example was subjected to autoclave molding of a carbon fiber epoxy composite prepreg (heating temperature Max: 180
° C), when used as a release film, both heat resistance and release properties were good. In addition, it was possible to distinguish from various materials used at the same time by coloring, and to observe the lower material by selection. Further, no red pigment was transferred to the contacting material.

Also, as a red pigment containing 98% by weight of ferric oxide,
Average particle size is 0.02μm, 2.0μm, 15.0 by sieving operation
When a film having a thickness of μm was processed and prepared in the same manner as in the above example (the concentration of the red pigment based on the fluoropolymer: 0.35% by weight), the results shown in Table 1 were obtained.

When the average particle size is 15.0 μm, the average particle size is 0.2
In order to obtain the same degree of coloration as that of the μm, it was necessary to increase the amount of the red pigment until its concentration with respect to the fluoropolymer became 1.5% by weight.

A film with an increased amount of pigment in this manner has poor transparency and makes it difficult to observe the lower part of the film, and the surface of the film becomes rough, so that it can be used as a mold release requiring a smooth surface finish. Did not.

The concentration of the red pigment in the fluoropolymer was 0.35.
When the raw material was 15.0 μm in weight% and the material was formed into a film, the extrusion system was dismantled and washed. Corrosion of the filter element progressed, and no corrosion inhibition effect was observed.

In addition, if a red pigment having a ferric oxide content of 85% by weight or more is used, as long as the average particle size of the red pigment is in the range of 0.05 to 10 μm, it can be practically used in terms of discrimination and transparency. there were.

In addition, the composition of the master pellet was changed so that the concentration of the red pigment with respect to the fluoropolymer was 0.05% by weight, 0.10% by weight,
Films prepared so as to be 2.0% by weight and 5.0% by weight, respectively, were processed into a film (the concentration of the red pigment with respect to the fluoropolymer: 0.35% by weight) in the same manner as in the above Examples. The result shown in FIG. (In the table, it is abbreviated as pigment concentration.) The concentration of the red pigment in the fluoropolymer is 0.05% by weight
When the average particle size was 0.2 μm, the raw material was formed into a film, and then the extrusion system was disassembled and washed. As a result, the filter element was corroded and no corrosion suppressing effect was observed.

As long as a red pigment having a ferric oxide content of 85% by weight or more is used, as long as the concentration of the red pigment with respect to the fluoropolymer is within the range of 0.1 to 2.0% by weight, transparency and All of the coloring degrees were practical.

[Effects of the Invention] According to the release film according to the present invention, by adjusting the average particle size of the red pigment and the concentration of the red pigment with respect to the fluoropolymer, a harmless ferric oxide is mainly used as the red pigment. Therefore, the release film can be made harmless, safe and can be handled naturally without consideration for hygiene and environmental maintenance.

In addition, since the corrosion of the extruder and peripheral equipment can be suppressed while using the fluoropolymer, the life of the equipment can be increased, the cost required for repair can be reduced, and the cost of the composite material can be reduced as much as possible. Now you can get it.

In addition, since the red pigment containing ferric oxide as a main component can exert a hiding power even in a small amount, it can be prevented from being transferred to a composite material and contaminated during molding, and the quality can be improved.

Claims (1)

(57) [Claims] 1. A fluorinated polymer containing at least 85% by weight of ferric oxide and having an average particle size of 0.05 to 10 μm.
And a concentration of the red pigment with respect to the fluoropolymer of 0.1 to 2.0% by weight.