JPS6361433B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for treating polyamide synthetic fibers with an adhesive, in particular a method for immersing polyamide synthetic fibers for reinforcing rubber molded articles in a water-soluble adhesive solution consisting of a resorcinol/formalin condensate. This relates to an adhesive treatment method that is subsequently heat-treated. (Prior art) Polyamide fibers that reinforce rubber molded products such as tires, conveyor belts, and hoses usually have a
After 500 to 3000 denier yarns consisting of 500 filaments are twisted or twisted together to form a cord, resorcin formalin latex (RFL) is applied to improve adhesion to rubber. A widely used method is immersion in an aqueous solution and heat treatment. However, when these methods are carried out, the adhesive-treated cord tends to become stiff due to penetration of the adhesive into the interior of the cord, solidification, and an increase in the packing density of the constituent filaments due to tension during heat treatment. Such an increase in hardness causes local stress concentration, which not only reduces strength and fatigue resistance, but also has a significant negative impact on workability in the process of molding tires and the like. Various methods have been proposed to improve the flexibility and strength retention of polyamide fibers treated with adhesives as described above. For example, there is an adhesive treatment method in which polyamide fibers are immersed in a specific urethane resin solution, dried under dry heat, and then immersed in an RFL aqueous solution for heat treatment (see Japanese Patent Application Laid-Open No. 1981-81686), and A method of applying a water-based emulsion oil to an undrawn polyamide fiber yarn and then passing it through an interlacer to generate uneven streaks on the surface of the yarn to improve the strength utilization after dipping (Japanese Patent Application Laid-Open No. 1989-1999) (See Publication No. 15052) has been proposed. Although the above-mentioned proposed treatment methods have improved flexibility or strength retention to some extent, the current situation is that they have not yet reached a satisfactory level. (Problems to be solved by the invention) In recent years, there has been a demand for tires to be lighter and have a longer running life, and with the increase in denier for process improvements, there has been a demand for improvements in the formability of green tires. As a result, improvements in the strength, flexibility, and fatigue resistance of treated cords have become particularly important for tire cords. However, the processing method proposed above requires complicated steps, and the performance described above is not sufficient. On the other hand, the resorcinol-formalin condensate, which is commonly used in the adhesive treatment of polyamide fibers, is condensed under an alkali catalyst, and in this case, the rate of methyl roll formation is faster than the rate of condensation reaction. Because it forms a condensate with fast methylolation and preferential methylolization, a resin film with high crosslinking density is formed when polyamide fibers are impregnated and heat treated, resulting in a fiber with low flexibility and strong strength. Also, the fatigue resistance does not meet the above requirements. (Means for Solving the Problems) This invention provides polyamide-based synthetic fibers in which resorcinol (R) and formalin (F) are mixed in a molar ratio (R/F).
A water-soluble non-thermosetting resorcinol/formalin condensate which is acidicly condensed with a ratio of 1/0.5 to 1/1;
A water-soluble adhesive consisting of formalin added so that the total amount of formalin is 0.9 to 1.6 moles per mole of resorcinol component of the condensate, caustic soda to adjust the pH to at least 7.0, rubber latex, and ammonia. This is a method for treating polyamide-based synthetic fibers with an adhesive, which is characterized by immersing them in water and then heat-treating them. The above resorcinol/formalin condensate (referred to as RF condensate) is composed of resorcinol (R) and formalin (F).
The RF condensate is acidic condensed at a molar ratio (R/F) of 1/0.5 to 1/1.
For example, products with an R/F of 1/0.6 are available under the trade name Penacolite R-2170 (manufactured by Cotpers) and Sumikanor 700 (manufactured by Sumitomo Chemical Industries, Ltd.), and products with an R/F of 1/1 are available under the trade name Aadhar. RF
(manufactured by Hodogaya Chemical Industry Co., Ltd.) is commercially available. Traditionally used to process polyamide synthetic fibers
The RF condensate blended into the RFL adhesive has an R/F of 1/1 to 1/3 and is condensed under an alkali catalyst such as caustic soda. Strength and fatigue resistance cannot be obtained. The formalin added to the above RF condensate is RF
The total amount of formalin is blended in such a manner that the total amount of formalin is 0.9 to 1.6 mol, preferably 1.0 to 1.4 mol, per 1 mol of resorcinase condensate. If the total formalin content is less than 0.9 mol, the flexibility will be improved and the cord strength will be high, but the cohesive force will be low and high adhesive strength will not be obtained.
Fatigue resistance is not improved, and strength and fatigue resistance are also lowered. Further, even if the R/F of the RF condensate is 1/1, a high adhesive cannot be obtained unless formalin is added. The latex may be one or a mixture of two or more latexes such as natural rubber, styrene-butadiene copolymer rubber, and styrene-butadiene-vinylpyridine copolymer. Caustic soda is added to facilitate the solubility of the RF condensate in water. In addition, ammonia ensures the storage stability of RFL adhesive (especially prevention of gelation), and the PH of RFL adhesive
7.0 or more, preferably 9.9 or more, more preferably
Adjusted to 10.0 or higher. The mixing ratio of RF condensate and latex is 1/4~
1/8 is preferable. RFL adhesives are used as aqueous solutions, and their solids concentration is preferably 10-30% by weight. The polyamide synthetic fiber of this invention is a filament yarn obtained by melt spinning and drawing polyamide such as nylon 6, nylon 66, and nylon 46.
Alternatively, the filament yarn is usually twisted singly or in a plurality of yarns. The polyamide fiber may contain a heat stabilizer, an antioxidant, an antistatic agent, an adhesion improver, etc., if necessary. The polyamide synthetic fiber is immersed in the RFL adhesive aqueous solution and then heat treated to attach RFL. The amount of solid particles attached to the polyamide cord is preferably 3 to 10% by weight. (Function) Since the RF condensate used in this invention is prepared using an acid such as sulfuric acid as a catalyst, the condensation reaction rate of the resulting RF condensate is faster than the methylolation rate, so it is linearly The result is a condensed, substantially thermoplastic resin. When polyamide-based synthetic fibers are impregnated with an RFL adhesive solution prepared by blending formalin and latex added to this resin in a strictly specified manner and heat-treated, the RFL resin forms a crosslinked network on the fibers. However, the added formalin regulates the crosslinking density to the minimum necessary limit, resulting in the formation of a flexible resin film with high cohesion, resulting in the treated fibers being highly flexible, strong, and fatigue resistant. This results in a significant improvement. (Example) The percentages and parts in the following experiments are expressed on a weight basis unless otherwise specified. Experiment 1 Mix 33.8 parts of RF condensate (R/F=1/0.6, 75% aqueous solution, trade name Penacolite R-2170), an arbitrary amount of 37% formalin, 3.47 parts of 20% caustic soda, and 406 parts of water and heat at 20°C. After aging for 6 hours in
% styrene-butadiene-vinylpyridine copolymer rubber latex (trade name: Piratex, manufactured by Sumitomo Naugatatsu Co., Ltd.) 310.9 parts, 49% styrene-butadiene copolymer rubber latex (trade name: J9049, manufactured by Sumitomo Naugatatsu Co., Ltd.) 86.8 parts, 28% aqueous ammonia
17.4 parts and water were added to prepare a total of six types of RFL adhesive treatment liquids with a solid content of 20%, including Examples 1 to 4 and Comparative Examples 1 and 2, each containing different amounts of formalin added.
After immersing a nylon 6 tire cord (1890 denier/2 strands twisted) in this treatment solution, the solid content was adjusted to 5% compared to the untreated tire cord, and then heated at 120°C for 2 minutes. Hot air dried under 1.5% tension. Next, after 8.5% tension for 60 seconds in heated air at 200℃,
A heat treatment was performed for 60 seconds in heated air at ℃ to obtain an adhesive-treated cord. The cutting strength of the untreated cord used at this time was 35.8 kg. Experiment 2 In Example 1 above, the RF condensate (R/F=
1/1, 43% aqueous solution, product name Aadhaar RF), and the amount of formalin added was changed.
A total of five types of adhesive treated cords, Examples 5 to 7 and Comparative Examples 3 and 4, were obtained in the same manner as in Example 1. Experiment 3 18.75 parts of resorcin, 27.65 parts of 37% formalin (R/F=1/2), 2.55 parts of 20% caustic soda, water
404.5 parts were mixed and aged at 20°C for 6 hours to produce a resol type RF initial condensate, which was then mixed with 41% styrene/vinylpyridine copolymer rubber latex 311.0
1 part, 86.7 parts of 49% styrene-butadiene copolymer rubber latex, 17.4 parts of 28% aqueous ammonia, and water to prepare an RFL adhesive treatment solution with a solid content of 20%.
Using this treatment solution, nylon 6 was treated in the same manner as in Example 1.
The tire cord was treated to obtain an adhesive treated cord of Comparative Example 5. Experiment 4 An adhesive treated cord of Comparative Example 6 was obtained by processing in the same manner as in Experiment 3 except that R/F=1/1.4 in Experiment 3. The results of measuring the physical properties of the treated cords of each of the above Examples and Comparative Examples are shown in the table below. In addition, among the physical properties, the bending hardness measure representing the cord flexibility is determined by the Gurley method, that is, the swing amplitude of a pendulum (load 25 g) when the length of the sample is 3.8 using the Gurley States Funestester (manufactured by Toyo Seiki Co., Ltd.). This is the value obtained. The adhesive strength is a value (Kg/cm) determined by the H test method. Fatigue resistance was determined by using a regular tube fatigue tester to create a tube fatigue test piece with dip cords embedded at a density of 25 cords/2.54 cm, bending angle 85 degrees, internal pressure 3.5 Kg/cm ² , and rotation speed.
The tube was fatigued at 860 rpm and the time until the tube broke was measured.

【table】

[Table] As shown in the table above, Comparative Example 1, in which the molar ratio of total formalin to 1 mole of resorcinol component is less than 0.9 mol, has poor adhesive strength and fatigue resistance, and the comparison example, in which the molar ratio of total formalin to 1 mol of resorcinol components is greater than 1.6. Example 2
And Comparative Example 4 has high bending hardness and poor fatigue resistance. Furthermore, even if the molar ratio of total formalin was greater than 0.9 mol, Comparative Example 3 in which formalin was not added had poor adhesive strength and fatigue resistance. Furthermore, Comparative Examples 5 and 6 in which the RF condensate R/F was 1/2 or 1/1.4 had high bending hardness, significantly inferior fatigue resistance, and low strength. (Effects of the Invention) The polyamide synthetic fiber according to the present invention has low bending hardness, excellent flexibility, high strength and adhesive strength with rubber, and excellent fatigue resistance. As a result, it is advantageous in the production process as a reinforcing material for rubber moldings.

Claims (1)

[Claims] 1 Polyamide-based synthetic fibers are treated with resorcinol (R)
and formalin (F) at a molar ratio (R/F) of 1/0.5.
A water-soluble non-thermosetting resorcinol/formalin condensate acidically condensed in a ratio of ~1/1, and the total amount of formalin per mole of the resorcinol component of the condensate.
Polyamide-based synthesis characterized by immersion in an aqueous adhesive solution consisting of Holimarin added to have a concentration of 0.9 to 1.6 mol, caustic soda to adjust the pH to at least 7.0, rubber latex, and ammonia, and then heat-treated. Adhesive treatment method for fibers.