JPS6250333A - Treatment for bonding aromatic polyamide fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber excellent in adhesion to rubber and fatigue resistance, by treating an aromatic polyamide fiber with an aqueous solution of an epoxy compound and drying and heat-treating the fiber. CONSTITUTION:An aromatic polyamide fiber containing 50mol% or below repeating units of formula I (wherein X is -Ar1- or a group of formula II or Ar1-2 are each an aromatic group) in the molecule is treated under an applied tension of 0.01-0.5g/d with an aqueous solution or dispersion of an epoxy compound of formula III (wherein Y is H or a group of formula IV, at least two groups of formula IV are present in the molecule and n>=2), dried at 160-200 deg.C and heat-treated at 240-270 deg.C for 50-200sec. This fiber is treated with a mixture containing a condensate obtained by reacting resorcinol with formaldehyde at a molar ratio of 1:1.0-1.5 in the presence of an alkali catalyst and a rubber latex at a weight ratio (in terms of solid matter) of 10-15:100 under an applied tension of 0.01-0.5g/d, dried at 160-200 deg.C and heat-treated at 210-260 deg.C for 60-150sec under an applied tension.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a method for adhesion treatment of aromatic polyamide fibers, in particular, a method for adhering aromatic polyamide fibers using an epoxy compound and a resorcinol-formaldehyde condensate/rubber latex mixed liquid (RFL liquid). The present invention relates to an adhesive treatment method which imparts to the fibers excellent properties in terms of adhesion to rubber and fatigue resistance in composites with rubber.

(Prior art) General formula % Formula % represents a group selected from the group, Ar and Ar2 are the same -
or a different aromatic group. ) A typical example of aromatic polyamide fibers containing 50 mol% or more of the repeating unit represented by
These include poly(1,4-benzamide), Compared to other natural and synthetic fibers, this aromatic polyamide fiber has high strength, high modulus, low heat shrinkage, high heat decomposition resistance, and excellent creep properties, and can be used for filament chips, cords, cables, etc. In the form of cord fabrics, canvas, etc., it exhibits unprecedented properties as a reinforcing material for rubber articles such as conveyor belts, air springs, rubber hoses, and tires.

However, although they have these excellent advantages, these fibers have significantly inferior bending fatigue resistance and adhesion to rubber compared to other fibers, which is thought to be due to their internal structure. It has drawbacks, and improvements have been strongly desired. As a method for improving such fatigue resistance, there is a study of the twisted structure, as described in the Journal of the Japan Institute of Fiber Science, Vol. 34, No. 8 T.
As described in 342-T348 (1978), studies have been conducted to impart flexibility to fibers using a copolymer structure.

On the other hand, regarding adhesion, it has been considered that the aromatic polyamide fibers are generally pretreated with an epoxy compound and then heat treated with a normal RFL liquid.
Special public 53-37467.54-6677.55-20
No. 853 and each publication PE.

(Problems to be Solved by the Invention) As described above, in order to improve the drawbacks of aromatic polyamide fibers, conventionally only methods of improving the fatigue resistance or adhesiveness level independently of each other have been considered, and At the same time, a method for comprehensive improvement has not yet been found. In most cases, improvements made through the introduction of twisted structures or copolymer components described above require sacrificing original characteristic values such as strength, modulus, and resistance to thermal decomposition.

This invention attempts to impart both excellent adhesiveness and fatigue resistance to aromatic polyamide fibers without sacrificing the above-mentioned original characteristic values.

(Means for Solving the Problems) In order to solve the above problems, the inventors of the present invention have made intensive studies, especially regarding pretreatment liquids and heat treatment methods, and have found that the above problems can be solved by an appropriate combination thereof. After confirming this, we have achieved this invention.

That is, this invention represents a group selected from the general formula [X-C-N) (1) H group, and Ar and Ar2 are the same -
or a different aromatic group. ) When adhering an aromatic polyamide fiber containing 50 mol% or more of the repeating unit represented by the following in its molecule, the fiber has the general formula, where n is an integer indicating the number of repeating units and is 2 or more.

) is treated with an aqueous solution or aqueous dispersion of an epoxy compound represented by
Heat-treated at 270°C for 50 to 200 seconds, and then reacted a condensate of resorcin and formaldehyde at a molar ratio of 1:1.0 to 1:1.5 in the presence of an alkali catalyst and a rubber latex liquid. It is characterized in that it is treated with a liquid mixture having a solid content weight ratio of 10:i00 to 15:100, dried at 160 to 200°C, and finally heat treated under tension at 210 to 260°C for 60 to 150 seconds. This is an adhesive treatment method for aromatic polyamide fibers.

Specific examples of aromatic polyamide fibers treated by the method of this invention include poly(1,4-benzamide), poly(1,4-benzamide), poly(1,4-benzamide),
, 4-phenylene terephthalamide), poly(1,3-
phenylene isophthalamide) or 1,4-phenylene terephthalamide-3,4'-diaminodiphenyl ether copolymer.

The epoxy compound used in this invention is represented by the general formula (3), where n is usually 2 to 10, but compounds having a larger value of n can also be used. Preferred specific examples of the epoxy compound include diglycerol triglycidyl ether, triglycerol tetraglycidyl ether, and tetraglycerol pentaglycidyl ether.

By treating aromatic polyamide fibers with an aqueous solution or dispersion of an epoxy compound (hereinafter simply referred to as "epoxy compound liquid"), the fibers can be impregnated with the liquid. The epoxy compound is prepared by dissolving it in water or dispersing it in water using a suitable surfactant.The concentration of the epoxy compound is:
Although it varies depending on the treatment method and the type of epoxy compound, it is usually preferably 2% by weight or less, and if the concentration is too high, uniform impregnation will not be possible.

Specific methods for treating aromatic polyamide fibers with epoxy compound liquid include methods such as dipping the fibers in the liquid, applying the liquid to the fibers using a doctor knife, etc., or spraying the fibers. Conventionally used impregnation methods are possible, and any suitable one can be used.

When aromatic polyamide fibers are treated with an epoxy compound liquid, the fibers are subjected to an appropriate tension, specifically 0. Old ~
It is preferable to process while applying a tension of 0.5 g/d. If the tension during treatment is less than 0.01 g/d, the epoxy compound liquid will penetrate between the internal filaments of the fiber cord and the epoxy compound will harden there, resulting in a decrease in fatigue resistance. If it exceeds 5 g/d, the epoxy compound liquid is prevented from penetrating and remains in the coating only on the cord surface layer filaments, and a sufficient adhesion surface area cannot be obtained, resulting in a decrease in adhesive force.

The aromatic polyamide fibers treated with the epoxy compound liquid as described above are then dried at a temperature of 160 to 200°C to remove moisture. Next, this fiber is 240-270
Heat treatment at ℃ for 50-200 seconds. Heat treatment temperature is 240℃
If the temperature is less than 0.degree. C., the reaction between the epoxy compound and the aromatic polyamide cord is not sufficient, and the reaction and hardening between the epoxy compounds occurs preferentially, resulting in a decrease in adhesive strength and fatigue resistance. If the heat treatment temperature exceeds 280°C, the adhesive functional group of the epoxy compound will be decomposed and lost, and not enough will remain, which will not only lower the adhesive level but also significantly lower the initial strength value of the fiber. Not suitable for practical use.

In addition, if the treatment time is less than 50 seconds, the reaction between the epoxy compound and the fibers will not be sufficient even if the treatment is carried out at 280℃, and if the treatment time is longer than 200 seconds, the reaction between the epoxy compound and the fibers will not be sufficient even if the treatment is carried out at a temperature of 240℃. The amount of epoxy compound decreases and sufficient adhesive strength cannot be obtained.

Next, processing using the RFL liquid will be described. In the RFL liquid used in this invention, if the molar ratio of formaldehyde to recincine is less than 1.0, the polymerization reaction will not proceed sufficiently, and if it exceeds 1.5, the two-dimensional polycondensation reaction will proceed too much. In either case, the adhesive strength decreases, and if it exceeds 1.5, the bending fatigue resistance also decreases.

If the solid content weight ratio of the resorcinol/formaldehyde condensate and the rubber latex liquid is less than 10:100, sufficient adhesive strength will not be obtained, and if it exceeds 15:loo, not only will sufficient adhesive strength not be obtained, but the fatigue resistance will deteriorate. It also gets worse.

As the rubber latex liquid, depending on the type of rubber to be bonded to the aromatic polyamide fiber, one of natural rubber latex or synthetic rubber latex such as styrene-butadiene rubber, styrene-vinylpyridine-butadiene copolymer rubber, or the like is used. A mixed latex of two or more types is used.

An example of a method for preparing RFL liquid is as follows.

Dissolve resorcin in a predetermined amount of soft water, add 0.1 to 0.3 mol of an alkali catalyst such as caustic soda, caustic potash, aqueous ammonia, or urea to 1 mol of resorcin, and then add formaldehyde in an amount within the above range. , aged for 6-10 hours at room temperature. A latex liquid corresponding to the solid content weight ratio in the above range is mixed into the aqueous solution thus obtained, the total solid content concentration is adjusted to within the range of 13 to 30% by weight, and the mixture is aged at room temperature for 14 hours or more. RFL liquid can be prepared by this.

As a method for treating aromatic polyamide fibers with RFL i, a dipping method, a coating method, a spray method, etc. can be used as necessary, as in the case of the epoxy compound liquid. Further, as described in the treatment with the epoxy compound liquid, it is preferable to apply a tension of 0.01 g/d to 0.5 g/d during the treatment, and the reason is the same as in the case of the epoxy compound.

After RFL treatment, the fibers are dried at 160-200°C to remove moisture and then heat treated under tension. If the heat treatment temperature is less than 210°C, even if the treatment time exceeds 150 seconds, it will not be possible to react sufficiently with the aromatic polyamide after the epoxy compound treatment, and if the heat treatment temperature exceeds 260°C, even if the treatment time exceeds 150 seconds, Even if it is less than that, the RFL liquid will deteriorate and harden, resulting in a decrease in adhesive strength and fatigue resistance. Note that the tension during the heat treatment may be under the conditions normally used.

The total amount of the epoxy compound and RFL after the final heat treatment is preferably 5 to 15 parts by weight as a solid content based on 100 parts by weight of the aromatic polyamide fiber.

(Examples) The present invention will be described in more detail below with reference to Examples and Comparative Examples.

In this example, the adhesion test and fatigue resistance test were conducted as follows.

Adhesion test After adhesion treatment, the cord is embedded in the unvulcanized compounded rubber,
Vulcanize at 145°C for 30 minutes at a pressure of 20 kg/cn (20 kg/cn), dig out the cord from the resulting vulcanizate, and make 80 c+n/
The cord was peeled off from the vulcanizate at a speed of 10 minutes, and the center value of the chart at that time was taken as the adhesive force (kgZ pieces) as the drag force.

Fatigue resistance test After adhesion treatment, 50 cords were driven in 15 cm each, and the first
As shown in the figure, a two-layer cord layer 1 was embedded in the unvulcanized rubber 2 used in the adhesion test and covered with a sample as shown in the figure.
Vulcanize at a pressure of g/c/, then apply a load of 150 kg from both ends to a pulley with a diameter of 20 [11].
A repeated strain of 000 times/hr was applied, and after 50 hours, the cord was removed, the cord closer to the pulley surface was taken out, the strength was measured, and the retention rate (%) of the strength of the treated cord was taken as a measure of fatigue resistance.

Examples 1 to 4, Comparative Examples 1 to 6 Poly(1,4-phenylene terephthalamide), manufactured by DuPont, trade name Kevlar (
A cord was created by twisting 1500 d of raw yarn using KEVL^R) with a first twist of 32 times/10cm and a final twist of 32 times/locm.

The epoxy compound liquid (-bath liquid) and RFL liquid (two-bath liquid) of Examples were prepared as follows.

A solution having the following composition was prepared using diglycerol triglycidyl ether as an epoxy compound.

(-Preparation of bath solution, referred to as Ll solution) Part by weight Caustic soda (10% aqueous solution) 0.14 Water
98.64RFL solution was prepared as follows. (Preparation of two-bath solution, referred to as L2 solution) 1 part heavy water 524.0 Lusorcin 15.12 Formalin (
37%) 16.72 Caustic soda (10% aqueous solution) 11.00566, 8
5 After aging this mixture for 8 hours, vinylpyridine-styrene-butadiene copolymer rubber latex (41%) was added to it.
33.15 parts by weight was added and aged for 18 hours.

A one-bath solution and a two-bath solution of a comparative example representing a conventional example were prepared as follows.

IPD 22 (-bath treatment liquid) Part by weight Caustic soda (10% aqueous solution) 1.0 Aerosol 0T (5% aqueous solution) 2.0 Water 85.02-Pyrrolidone 10.0100,0 D5A (Two-bath treatment liquid) Part by weight water 222.4 Resorcinol 11.0 Formaldehyde (37% aqueous solution) 16.2 Caustic soda (1,
After aging this mixture for 8 hours, vinyl pyridine and styrene-butadiene copolymer rubber latex (41%) was added to it.
44.0 parts by weight, 61.1 parts by weight of water, aqueous ammonia (
11.4 parts by weight of 28% concentration) were added and aged for 8 hours.

Using the above code and using the above treatment liquid and treatment conditions as shown in Table 1, the treatment was carried out in the order of one bath and then two baths using a Rischler Co., Ltd. Combutreator, and this treatment code was used to form a rubber compound A as shown below. or 2 having the composition and rubber physical properties of B
A fiber rubber composite was made by combining the various rubbers as shown in Table 1, and the adhesion test and fatigue resistance test were conducted on the composite. The results are shown in Table 1.

Rubber compound A Part by weight Natural rubber 80 Styrene butadiene rubber 2011AF carbon black
50 stearic acid 2
70 Mustard oil 4 Zinc white
6N-phenyl-β-naphthylamine 1.5 sulfur
5.0 Rubber compound B Part by weight Natural rubber 80 Synthetic polyisoprene rubber 20 HAF carbon black
45 Silica 5 Stearic acid 2 Resorcinol
3 aroma oil
2 Zinc white 6N-
Phenyl-β-naphthylamine 1.5 Hexamethoxymethylmelamine 1.0 Sulfur
5.01 Glycerin diglycidyl ether, one component of PD22, has the general formula (■) where n-1 and Y are 3.
This is the case where Y is H. When such a bath liquid is used, adhesive strength and fatigue resistance are poor as shown in Comparative Examples 1 and 2. In addition, when resorcinol is added to rubber (
Comparative Example 3) also improved the adhesion level, but the fatigue resistance was poor.

Furthermore, even when Ll bath and L2 bath conforming to the present invention are used, if the temperature and time of the heat treatment zone do not satisfy the predetermined conditions (Comparative Examples 4.5 and 6), both adhesive strength and fatigue resistance cannot be satisfied at the same time.

Furthermore, if the tension during bath treatment exceeds 0.5 g/d, sufficient adhesion and fatigue resistance cannot be obtained.

(Effects of the Invention) As explained above in Examples and Comparative Examples, the present invention impregnates aromatic polyamide fibers with a specific epoxy compound liquid and then with an RFL liquid of a specific composition, and furthermore, after each impregnation, drying is performed. By heat treatment under specific conditions, rubber
It was possible to achieve excellent adhesion of the fibers and excellent fatigue resistance of the fibers.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a sample for fatigue resistance testing.

Claims (1)

[Claims] 1. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, X represents a group selected from the group consisting of -Ar_1- and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ , Ar_1 and Ar_2
are the same or different aromatic groups. ) When adhering aromatic polyamide fibers containing 50 mol% or more of repeating units in the molecule, the fibers are treated with the general formula ▲mathematical formula, chemical formula, table, etc.▼ (in the formula, Y is ▲mathematical formula, There are chemical formulas, tables, etc. ▼ Indicates a group or a hydrogen atom, and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ At least two groups exist in the molecule, and n is an integer that indicates the number of repeating units and is 2 or more. ) is treated with an aqueous solution or aqueous dispersion of an epoxy compound represented by
Heat treatment at 0 to 270°C for 50 to 200 seconds, then mix resorcin and formaldehyde in a ratio of 1:1.0 to 1:1.5.
Treated with a mixture of a condensate reacted in the presence of an alkali catalyst and a rubber latex liquid with a solid content weight ratio of 10:100 to 15:100, and dried at 160 to 200°C, A method for adhesion treatment of aromatic polyamide fibers, which is finally heat-treated under tension at 210 to 260°C for 60 to 150 seconds. 2. Treatment with an aqueous solution or aqueous dispersion of an epoxy compound and treatment with a mixture of the condensate and rubber latex liquid are performed while applying a tension within the range of 0.01 to 0.5 g/d to the aromatic polyamide fiber. A method according to claim 1. 3. The method according to claim 1, wherein Ar_1 and Ar_2 are both phenylene groups. 4. Aromatic polyamide fibers include poly(1,4-benzamide) and poly(1,4-phenylene terephthalamide)
, poly(1,3-phenylene isophthalamide), or 1,4-phenylene terephthalamide-3,4'-diaminodiphenyl ether copolymer. 5. The method according to claim 1, wherein the epoxy compound is diglycerol triglycidyl ether, triglycerol tetraglycidyl ether or tetraglycerol pentaglycidyl ether.