JPH0571701B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for treating aromatic polyamide fibers, in particular, treatment with an epoxy compound and treatment with a mixed liquid of resorcin formaldehyde condensate/rubber latex, which improves adhesion to rubber articles and mechanical fatigue resistance of the fibers. The present invention relates to a method for processing aromatic polyamide fibers with excellent properties. (Prior art) Aromatic polyamide fibers are fibers that have a compound structure represented by the general formula () in their molecules, and a typical example is poly(1,4-benzamide) when X is Ar ₁ . ,X is

Poly(1,4-phenylene terephthalamide) and poly(1,3-phenylene isophthalamide) in the case of [Formula],
Aromatics are linear polymers that have an amide bond and an aromatic group in the molecule, such as 1,4-phenylene terephthalamide-3,4'-diaminodiphenyl ether copolymer, which has a copolymer structure. These fibers are made from polyamide group polyamides. This aromatic polyamide fiber has much more stable mechanical properties than other organic synthetic fibers, such as aliphatic polyamide fibers or polyester fibers, with high strength, high modulus, and superior creep properties. Because of its properties and excellent heat resistance, it is useful as an industrial reinforcing material for reinforcing rubber articles such as tires, conveyor belts, air springs, rubber hoses, etc. in the form of filament chips, cords, cables, cord fabrics, canvas, etc. In recent years, its usefulness has been on the rise. On the other hand, although it has the above-mentioned advantages, the aromatic polyamide fiber has the disadvantage that its adhesion and fatigue resistance are extremely inferior to other organic synthetic fibers, and these disadvantages are particularly important in tires, conveyor belts, etc. Since this is a fatal defect as a reinforcing material for rubber articles such as air springs, improvement of the above-mentioned defect is strongly desired. Incidentally, one possible reason for the poor fatigue resistance of aromatic polyamide fibers is that these fibers have microfibrils with high molecular orientation and columnar crystal morphology, and have a microstructure with extremely high crystallinity. Because of this, they lack flexibility, and when mechanical stimuli such as repeated stretching and compression are applied to these fibers, buckling and associated rupture occur due to stress relaxation phenomena, and fatigue fracture accompanied by fibrillation occurs. This is something that can easily occur. Conventionally, in order to improve this drawback of poor fatigue resistance, methods such as examining the twisted structure, copolymerizing with a monomer that imparts flexibility, or introducing a flexible polymer into the fiber molecule, etc. A study was conducted. The results of the study on the copolymerization are published, for example, as "Microstructure and mechanical properties of polyparaphenylene terephthalamide copolymer fibers", Journal of the Japan Institute of Fiber Science, Vol. 34, No. 8, T342.
~T348 (1978), and as “Structure and physical properties of wholly aromatic nylon copolymers”, Journal of the Japan Institute of Textile Technology, No. 35.
Volume, No. 1, T13-T18 (1978). Furthermore, the adhesion of aromatic polyamide fibers is extremely inferior to that of aliphatic polyamide fibers, such as 6-nylon, because the former fibers exhibit higher molecular orientation and higher crystallinity. This is because it has a fine structure. For example, some RFL adhesives, which are a mixture of resorcinol, formaldehyde initial condensate, and rubber latex, have a sufficiently satisfactory bonding force when bonding synthetic fibers such as nylon and rubber. Adhesion to rubber was not successful and almost no adhesive strength was observed. This is due to the dense microstructure of aromatic polyamide fibers as mentioned above, which causes almost no bonding, including primary and secondary bonds, between these fibers and the RF component (resorcinol/formaldehyde condensate) in RFL. This is because no bond occurs. Therefore, Special Publication No. 53-37467, Special Publication No. 45-
As shown in No. 6677 and Japanese Patent Publication No. 55-20853, before treating aromatic polyamide fibers with RFL, the surface of the fibers is treated with an appropriate reagent in advance to form a bond with RFL on the surface. Methods have been proposed to introduce possible functional groups or molecules to improve adhesion. Further, Japanese Patent Publication No. 54-40115 discloses a method of treating aromatic polyamide fibers with an adhesive in which a special chemical is added to RFL. (Problems to be Solved by the Invention) As mentioned above, in the use of aromatic polyamide fibers for rubber products, there are two problems in particular: improving fatigue resistance and adhesion to rubber. However, in terms of improving fatigue resistance, conventional attempts, including attempts to change the twist structure and add flexibility, have not significantly reduced the strength of the fibers or
This was completely unsatisfactory since the other advantages of this fiber were lost. In addition, in terms of improving adhesiveness,
Pretreatment of fibers as seen in Japanese Patent Publication No. 54-6677 and Japanese Patent Publication No. 20853 of 1982 was also
None of the adhesives found in Publication No.-40115 provide satisfactory adhesion. Therefore, for aromatic polyamide fibers,
At present, no method has been found for imparting satisfactory fatigue resistance and adhesion. (Means for Solving the Problems) The present inventors have conducted extensive research in order to solve the above-mentioned problems of aromatic polyamide fibers, that is, to simultaneously improve fatigue resistance and adhesion. It has been confirmed that the above object can be achieved by treating with an epoxy compound and then treating with a resorcinol-formaldehyde condensate/rubber latex mixture, thereby achieving the present invention. That is, this invention has the general formula

[Formula, X is Ar ₁ or

[Formula], Ar ₁ and Ar ₂ are the same or different aromatic groups, and m is a positive integer indicating the number of repeats. ) Aromatic polyamide fibers containing 50% or more of monomer repeating units represented by Glycidyl ether is reacted and fixed by surface treatment, and then this reaction product is reacted with resorcin and formaldehyde at a molar ratio of 1:1.0 to 1:1.5 in the presence of an alkali catalyst. :
The adhesion amount after drying of the mixed solution in a weight ratio of 100 to 15:100 to 100 parts by weight of aromatic polyamide fibers is 4.
This is a method for treating aromatic polyamide fibers, in which the fibers are deposited in an amount of ~12 parts by weight and then heat-treated at a high temperature of 200° C. or higher, thereby achieving the above object. As the aromatic polyamide fiber, X in the formula is Ar ₁ ,

[ka] and X in the equation

[Formula] is,

[Image Omitted] is used, among which, in the case of the formula, poly(1,4-benzamide is preferred; in the case of the formula,
Poly(1,-4-phenylene terephthalamide) and poly(1,3-phenylene isophthalamide) are preferred, and 1,4-phenylene terephthalamide-3, which contains 50% or more of repeating units of the formula in the molecule. Also preferred are 4'-diaminodiphenyl ether copolymers. In addition, in this invention, the epoxy compounds of diglycerol triglycidyl ether, triglycerol tetraglycidyl ether, and tetraglycerol pentaglycidyl ether are reacted and fixed to the aromatic polyamide fiber, but the amount of this reaction and fixation is It is specified that the amount is 0.05 to 0.3 parts by weight per 100 parts by weight. The amount of reaction and fixation is an important condition for achieving the purpose of the present invention, and if it is less than 0.05 parts by weight or more than 0.3 parts by weight, the adhesion to rubber may decrease or the aromatic polyamide fibers may Fatigue resistance deteriorates and the object of the invention cannot be achieved. In order to react and fix an epoxy compound to aromatic polyamide fibers, the epoxy compound can be dissolved in water as it is, or it can be solubilized in water using an appropriate surfactant, and the fibers can be immersed in the resulting aqueous solution. Preferably, the epoxy compound is reacted and fixed on the surface of the fiber in an appropriate amount within the above range by spraying the aqueous solution onto the fiber and then heat-treating the fiber at a temperature of 200° C. or higher. In this case, the amount of the epoxy compound can be controlled by controlling the amount of the catalyst that opens the epoxy group of the epoxy compound, the concentration of the epoxy compound in the aqueous solution, the ratio of the amount of the aqueous solution to the fiber, the heat treatment temperature and time, etc. Just choose the optimal conditions. A mixed solution of resorcin formaldehyde condensate and rubber latex used in this invention (hereinafter referred to as
(referred to as RFL liquid) is caustic soda, caustic potash,
Add 0.1 to 0.3 mol of an alkali catalyst such as ammonium hydroxide or urea to 1 mol of resorcin, and react the resorcin and formaldehyde at a molar ratio of 1:1.0 to 1.5 at room temperature for several hours, preferably 6 to 10 hours. The resulting resorcin formaldehyde condensate was mixed with the rubber latex liquid at a specific gravity ratio of 10:100.
It can be obtained by mixing at a ratio of 15:100 to 15:100 and further aging at room temperature for several hours, preferably 14 hours or more. In contrast to the above RFL liquid used in this invention, D5A, which is a generally well-known resorcinol-formaldehyde condensate liquid, has a molar ratio of resorcinol and formaldehyde of 2.0 and a polymerization ratio of resorcinol-formaldehyde condensate and rubber latex of 20:100. It is an adhesive. The RFL liquid of this invention has superior permeability to aromatic polyamide fiber cords and fiber cords treated with epoxy compounds compared to general resorcin formaldehyde/rubber latex liquids such as D5A, and can be obtained by evaporating the liquid. The resulting film itself has even higher strength and modulus. The rubber latex used in the RFL liquid of this invention may be one of natural rubber latex, synthetic rubber latex such as styrene-butadiene copolymer rubber, styrene-vinylpyridine-butadiene copolymer rubber, or a mixed latex of two or more of the above-mentioned rubber latexes. Generally, the type of latex is selected depending on the type of rubber that adheres to the aromatic polyamide fiber. Methods for attaching the RFL liquid to aromatic polyamide fibers to which an epoxy compound has been reacted and fixed include methods of immersing the fibers in RFL liquid, RFL
A method of applying the liquid to the fibers with a doctor knife, etc.
Or how to spray RFL liquid on the fibers, etc.
It can be selected appropriately depending on the need. When applying the RFL liquid, the amount of the RFL liquid to be applied is preferably controlled to 4 to 12 parts by weight based on the dry RFL liquid solids based on 100 parts by weight of the aromatic polyamide fiber. If it is less than 4 parts by weight, the adhesiveness with rubber will be low, and if it exceeds 12 parts by weight,
This is because although the adhesion properties hardly change, the fatigue resistance of the fibers decreases. After attaching the RFL liquid to the fibers as described above,
By heat-treating this fiber at a temperature of 200 to 270°C for 30 to 240 seconds, an aromatic polyamide fiber for reinforcing rubber articles with excellent adhesiveness and fatigue resistance can be obtained. (Examples) The present invention will be described in more detail below with reference to Examples. Example 1 Poly(1,4-
Phenylene terephthalamide) (manufactured by DuPont, trade name KEVLAR)
Using this method, the 1500d raw yarn was twisted with 32 twists/10cm for the first twist and 32 times/10cm for the final twist to create a cord with a twist structure of 1500d/2. A liquid having the following composition was prepared using diglycerol triglycidyl ether as an epoxy compound. Parts by weight Diglycerol triglycidyl ether 1.20 Sodium dioctyl sulfosuccinate (70
%) 0.02 Caustic soda (10% aqueous solution) 0.14 Water 98.64 The cord was immersed in this epoxy compound aqueous solution using a Ritzler computer reactor, and then passed through a drying oven at 160°C for 60 seconds and heated at 240°C. ×60 seconds heat treatment furnace and further RFL
Immerse in liquid. The RFL liquid has the following composition: Water 524.01 Resorcinol 15.12 Formalin (37%) 16.72 Caustic soda (10% aqueous solution) 11.00 Total 566.85 After aging the mixture at room temperature for 8 hours, this is mixed with vinylpyridine styrene butadiene copolymer rubber latex (41%). 433.15 parts by weight was added and further aged for 16 hours. The cord immersed in this RFL liquid was heated to 160°C
After passing through a drying oven for 69 seconds, it was passed through a heat treatment oven at 240°C for 60 seconds to obtain an adhesive-processed cord. The amount of the epoxy compound reacted and adhered to the cord and the amount of the RFL liquid solid component attached to the cord were 0.1 and 8 parts by weight, respectively, based on 100 parts by weight of the cord. The adhesive strength of the cord to rubber is determined by embedding the adhesive-treated rubber cord in the following unvulcanized compounded rubber composition and vulcanizing it at 145°C for 30 minutes under a pressure of 20 kg/ ^cm2 .
Dig out the cord from the resulting vulcanizate, 30 per minute
The cord was peeled off from the vulcanizate at a speed of cm, and the peeling effect was measured, which was defined as the adhesive strength (Kg/piece).
The unvulcanized compounded rubber composition is as follows. Parts by weight Natural rubber 80 Styrene-butadiene copolymer rubber 20 Carbon black 40 Stearic acid 2 Petroleum softener 10 Pine tar 4 Zinc white 5 N-phenyl-β-naphthylamine 1.5 2-benzothiazole disulfide 0.75 Diphenylguanidine 0.75 Sulfur 2.5 Next, the fatigue resistance of the obtained cord was determined by driving 50 cords/5cm and pasting the above-mentioned unvulcanized compound rubber 0.5mm sheet from both sides, 5cm wide x 60cm.
A long topping cord sheet was prepared. Next, the topping cord sheets prepared above were pasted on both sides of a 3 mm thick, 5 cm wide x 60 cm long unvulcanized compound rubber, and the topping cord sheets prepared above were then attached to both sides so that the total thickness of the sample was 15 mm. The unvulcanized compounded rubbers were bonded together and vulcanized at 145°C for 30 minutes under a pressure of 20 kg/cm ² to produce a vulcanized product for fatigue resistance measurement. Next, this vulcanized product was placed on a pulley with a diameter of 20 mm, a load of 150 kg was applied from both ends, and bending strain was applied 5000 times per hour. After 50 hours, the vulcanized product was removed, the cord closest to the pulley surface was taken out, and its breaking strength was evaluated. The fatigue resistance of the cord was expressed as a percentage of the original breaking strength of the cord. Table 1 shows the adhesive strength and fatigue resistance of the cord of Example 1.

[Table] Example 2 As the aromatic polyamide fiber of Example 1, 1,
4-Phenylene terephthalamide-3.4'-diaminodiphenyl ether copolymer (trade name manufactured by Teijin)
The same procedure as in Example 1 was carried out except that HM-50) was used. Adhesive strength and fatigue resistance are shown in Table 1. Example 3 The same procedure as in Example 1 was carried out except that the epoxy compound in Example 1 was replaced with triglycerol tetraglycidyl ether. Adhesive strength and fatigue resistance are shown in Table 1. Example 4 The same process as in Example 1 was carried out, except that the amount of the epoxy compound in Example 1 that was reacted and fixed was 0.05 parts by weight per 100 parts by weight of aromatic polyamide fibers. Table 1 shows the adhesive strength and fatigue resistance obtained. Example 5 The epoxy compound of Example 1 was changed to tetraglycerol pentaglycidyl ether, and the amount of reaction and fixation was 0.2 per 100 parts by weight of aromatic polyamide fiber.
The same procedure as in Example 1 was carried out except that the parts by weight were adjusted. Adhesive strength and fatigue resistance are shown in Table 1. Comparative Example 1 The procedure of Example 1 was repeated, except that D5A was used as a commonly used resorcinol formaldehyde condensate solution prepared as follows in place of the RFL solution of Example 1. D5A is made by aging a mixture of the following composition: Parts by weight Water 222.4 Caustic soda (1.67%) 17.9 Resorcinol 11.0 Formaldehyde (37%) 16.2 267.5 at room temperature for 6 hours, and then the following ingredients: Parts by weight Vinylpyridine-styrene-butadiene copolymer rubber latex (41%)
244.0 Water 61.1 Ammonium hydroxide (28%) 11.4 was added (1000 parts by weight in total), and the mixture was further heated for 8 hours. Adhesive strength and fatigue resistance are shown in Table 1. Comparative Example 2 The same procedure as in Example 1 was carried out, except that an epoxy compound of the following formulation was used instead of the aqueous solution of the epoxy compound in Example 1, and RFL of Comparative Example () was used. Part by weight Glycerin diglycidyl ether 2.0 Caseida (10%) 1.0 Aerosol OT (5%) 2.0 Water 85% 2-pyrrolidone 10.0 100.0 The amount of glycerin diglycidyl ether reacted and fixed to the aromatic polyamide fiber is The amount was 0.2 parts by weight per 100 parts by weight. The results are shown in Table 1. Comparative Example 3 The same procedure as in Example 1 was carried out, except that the reaction and fixation amount of the epoxy compound of Example 1 to 100 parts by weight of aromatic polyamide fibers was 0.6. Table 1 shows the adhesive strength and fatigue resistance of this cord. Comparative Example 4 The same procedure as in Example 1 was conducted except that a solution obtained by removing diglycerol triglycidyl ether from the aqueous solution of the epoxy compound of Example 1 was used. The amount of epoxy compound reacted and fixed was 0. Comparative Example 5 The RFL liquid of Example 1 was applied to aromatic polyamide fibers.
The same procedure as in Example 1 was carried out except that the amount of adhesion after drying was 3 parts by weight based on 100 parts by weight. Adhesive strength and fatigue resistance are shown in Table 1. Comparative Example 6 The RFL liquid of Example 1 was applied to aromatic polyamide fiber.
The same procedure as in Example 1 was carried out except that the amount of adhesion after drying was 15 parts by weight based on 100 parts by weight. Adhesive strength and fatigue resistance are shown in Table 1. (Effects of the Invention) As explained above in the Examples and Comparative Examples, the present invention involves reacting and fixing diglycerol triglycidyl ether, triglycerol tetraglycidyl ether or tetraglycerol pentaglycidyl ether to aromatic polyamide fibers, and then resorcin formaldehyde condensate,
By heat-treating a predetermined amount of the rubber latex mixture, it was possible to simultaneously improve fatigue resistance and adhesion to rubber, which were major problems in the use of aromatic polyamide fibers in rubber products.

Claims (1)

_[ Claims _] 1 _General formula [Formula] (wherein, 0.05 to 0.3 parts by weight of diglycerol triglycidyl ether or triglycerol tetraglycidyl ether per 100 parts by weight of aromatic polyamide fibers containing 50% or more of monomer repeating units represented by (an integer) in the molecule. Alternatively, tetraglycerol pentaglycidyl ether is reacted and fixed by surface treatment, and then this reaction product is reacted with resorcin and formaldehyde at a molar ratio of 1:1.0 to 1:1.5 in the presence of an alkali catalyst. With rubber latex liquid
A mixed solution with a weight ratio of 10:100 to 15:100 is applied to 100 parts by weight of aromatic polyamide fiber in an amount of 4 to 12 parts by weight after drying, and this is heat-treated at a high temperature of 200°C or higher. A method for processing polyamide fibers characterized by: 2. The method according to claim 1, wherein Ar ₁ and Ar ₂ in the general formula are: 3 The aromatic polyamide fiber is poly(1,4-benzamide), poly(1,-4 phenylene terephthalamide), poly(1,3-phenylene isophthalamide) or 1,4-phenylene terephthalamide-3, The method according to claim 1, which is a 4'-diaminodiphenyl ether copolymer.