JPH0720621B2 - Unvulcanized rubber sheet Polyester film for release - Google Patents

Description

TECHNICAL FIELD The present invention relates to a base material for molding an unvulcanized rubber sheet, and more specifically, a release base material for molding an undertread rubber (liner) mainly for automobile tires. It is about.

[Prior Art] As a base material for molding an unvulcanized rubber sheet, (a) a fabric made of polyester fibers or polypropylene fibers coated with or impregnated with a release agent such as silicon (liner cloth).

(B) A polyethylene film laminated on the woven fabric according to the item (a).

(C) Polyethylene film.

It has been known.

[Problems to be Solved by the Invention] However, the conventional unvulcanized rubber sheet molding base material has the following problems.

Regarding the base material in (a), the rubber activity is reduced by blooming (precipitation of rubber chemicals), and the release agent is transferred to the rubber sheet (particularly, the transfer of silicone to the rubber sheet is caused by the tread portion of the tire). Problems such as adhesive failure in the laminating process (vulcanization adhesion)), quality at the time of manufacturing thin rubber sheet due to surface properties (texture) and process stability (thickness accuracy, release trouble) etc. Yes, regarding the base materials in (b) and (c), the molding temperature of the rubber sheet (100 to 130
(C)) causes wrinkles caused by poor heat resistance and stretches, which causes poor surface properties of molded rubber sheets and poor thickness accuracy (especially in the case of thin rubber sheets), which is important in terms of automobile tire quality. There is a limit in improving the roundness as an element related to the above, in the reliability of airtightness in the tubeless tire which has become the mainstream in recent years, and also in the process workability and the reduction of the defective rate.

The present invention solves these problems, is excellent in both heat resistance and surface properties, and has no adhesion failure during vulcanization adhesion due to transfer of a release agent to a rubber sheet. The purpose is to provide.

[Means for Solving Problems] In the present invention, at least one compound selected from the group consisting of fatty acids, fatty acid amides, ester waxes, and metallic soaps is blended in a 0.03 wt% to 3 wt% polyester film. The present invention relates to a polyester film for release of an unvulcanized rubber sheet, which is characterized in that

Fatty acids in the present invention include stearic acid, myristic acid, palmitic acid, arachidic acid, behenic acid, etc., and fatty acid amides include stearyl amide, palmityl amide, oleyl amide, methylene bis stearoamide, ethyne. Lenbis stearamide and the like,
Ester waxes include natural waxes such as carnauba wax (ester of myricyl alcohol and cerotic acid), ibotaro wax, montan wax, and synthetic wax such as wax synthesized from behenic acid and branched alcohol having 24 carbon atoms. Examples of the metallic soaps include lead stearate, calcium stearate, cadmium stearate, zinc laurate, calcium laurate and the like.

Among these, alkylene fatty acid bisamides are preferably used, and ethylene bis stearamide is more preferable, from the viewpoints of releasing effect, quality stability of molded rubber sheet, hygiene, and raw material cost.

The polyester film is composed of an ester-forming dicarboxylic acid component having terephthalic acid as a main constituent and an ester-forming diol component having ethylene glycol as a main constituent. Direction), the tensile stress at 2% elongation (hereinafter abbreviated as F-2 value) determined from the stress-strain curve at 120 ° C exceeds 1 kg / mm ² , preferably 1.5 kg.
/ mm ² or more. F-2 value at 120 ℃ is 1kg / m
If it is m ² or less, it is not preferable because defects such as poor dimensional stability of the rubber sheet due to elongation of the molding base material occur in the rubber sheet molding step.

If necessary, a pigment such as titanium white and other additives may be added.

The compounding amount of the compound with respect to the polyester film,
0.03 to 3.0 wt% is preferable, more preferably 0.04 to 2.5 wt
%, And more preferably 0.05 to 2.0 wt%, and those within this range have stable release effect in rubber sheet molding, and the migration of the compound to the molded rubber sheet is minute, and the quality is excellent. Is obtained.

When the compounding amount of the compound is less than 0.03 wt%, the releasing effect becomes unstable, while when it exceeds 3 wt%, the blooming amount of the compound on the surface of the polyester film increases. As a result, the amount of the compound transferred to the unvulcanized rubber sheet increases, and in the bonding step with the tread portion and other portions of the tire, adhesion failure occurs, and at the same time, the unvulcanized rubber sheet of the present invention is released from the mold. The heat resistance of the polyester film for use is lowered, which is not preferable.

Next, a method for producing the polyester film for releasing the unvulcanized rubber sheet of the present invention will be described.

When a polyester film is formed using a polyester resin obtained by polycondensing a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component by a conventional method, An unstretched film was obtained using a T-die after mixing and mixing at least one kind and a stabilizer such as a coloring agent such as titanium white and an antioxidant as necessary. Then, this was stretched in the machine and transverse directions at a temperature of Tg or higher and a melting temperature or lower to obtain a biaxially stretched film. In addition, in the production of the base material for molding the unvulcanized rubber sheet, a laminated film by coextrusion may be used.

In addition, the compound in the present invention may be compounded in either a solid phase or a liquid phase, or may be compounded at the stage of polycondensation of the polyester resin.

[Characteristics Measuring Method and Effect Evaluation Method] Tensile stress (F-2 value) at 2% elongation at 120 ° C. According to ASTM D882, it was measured at a temperature condition of 120 ° C. ± 1 ° C.

Releasability Nipol BR1200 ^* 100 parts ^* Nippon Zeon's butadiene rubber Zinc white 3.0 parts Stearic acid 2.0 parts HAF carbon black 50 parts Sulfur 1.8 parts A rubber sheet with a thickness of 5 mm is formed with the above composition, and this is used in the present invention. An unvulcanized rubber sheet was subjected to a contact treatment on a release polyester film under the conditions of 12.5 kg / cm ² and 120 ° C for 15 minutes, and then cooled to room temperature to prepare a sample piece having a width of 24 mm and a length of 150 mm. . Next, this sample was peeled off at a peeling angle of 180 using a Shopper type tensile tester manufactured by Daiei Chemical Seiki
The peeling force was measured at a pulling speed of 300 mm / min.

In addition, the releasability was determined according to the following criteria.

Peeling force (g / 24mm) Judgment 100 or less ◎ 100 to 130 ○ 130 or more × Blooming A rubber film after the peeling force measurement in the previous section was coated with a normal polyester film (Toray "Lumirror" T60 38μ thickness) at room temperature for 12.5 After the materials were brought into close contact with each other at a pressure of kg / cm ² , the peeling force was measured in the same manner as in the releasability measuring method described in the preceding paragraph, and judged according to the following criteria.

Peeling force (g / 24 mm) judgment 150 or more ◎ 130 to 150 ○ 130 or more × [Example] Examples of the present invention will be described below.

Example 1 Polyethylene terephthalate resin was obtained by polycondensation of terephthalic acid and ethylene glycol by a conventional method.
Then, in producing a polyester film using this, the polyethylene terephthalate resin was previously blended with 5% by weight of ethylenebisstearamide, so-called master pellets were used, and the final concentration was adjusted to 0.05% by weight. An unstretched film was obtained by the T-die method. Next, this unstretched film was stretched 3.3 times in each of the machine direction and the transverse direction and heat-set to obtain a 38 μ biaxially stretched film. The results are shown in the table.

Examples 2 to 5 A 38 µm film was obtained in the same manner as in Example 1 except that the type and compounding amount of the compound was changed. The results are shown in the table.

Comparative Examples 1 to 3 38 μm films were obtained in the same manner as in Example 1 except that the types and blending amounts of the compounds were changed. The results are shown in the table.

[Effects of the Invention] The unvulcanized rubber sheet releasing polyester film according to the present invention has excellent releasability, blooming property (compounding agent) in combination with excellent dimensional stability, mechanical properties and surface property of the polyester film. It is a film that is excellent in both of (adhesion failure at the time of vulcanization adhesion due to transfer to the rubber surface), and the quality of the unvulcanized rubber sheet can be dramatically improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08L 67/02 LNZ B29K 21:00 105: 24 B29L 7:00

Claims (2)

[Claims] 1. A polyester film containing 0.03 wt% to 3 wt% of at least one compound selected from the group consisting of fatty acids, fatty acid amides, ester waxes, and metallic soaps. Vulcanized rubber sheet Polyester film for release. 2. The polyester film for releasing an unvulcanized rubber sheet according to claim 1, wherein the compound is an alkylenebisfatty acid amide.