AU4982393A

AU4982393A - Water-containing aromatic polyamide pulp and process for producing the same

Info

Publication number: AU4982393A
Application number: AU49823/93A
Authority: AU
Inventors: Kosaku Asagi; Shigenao Hata; Tatsuya Koizumi
Original assignee: Akzo Nobel NV
Current assignee: Akzo Nobel NV
Priority date: 1992-09-02
Filing date: 1993-09-01
Publication date: 1994-03-29
Anticipated expiration: 2013-09-01
Also published as: CA2143630A1; DE69309077T2; EP0658226B1; AU673691B2; KR950703099A; DE69309077D1; WO1994005854A1; EP0658226A1; ATE150501T1

Abstract

A water-containing aromatic polyamide pulp which has been surface-treated with an epoxy resin and has a water-content of 30 to 95 % by weight. This pulp is produced by dispersing an aromatic polyamide pulp in an aqueous epoxy resin emulsion, filtering the mixture and then dehydrating the pulp separated.

Description

DESCRIPTION

WATER-CONTAINING AROMATIC POLYAMIDE PULP AND PROCESS FOR PRODUCING THE SAME

Technical Field

This invention relates to a water-containing aromatic polyamide pulp surface-treated with an epoxy resin and to a process for producing the same. More particularly, it relates to a water-containing aromatic polyamide pulp which is suitable to uses requiring a step of dispersing aromatic polyamide pulp in water to make paper as in the production of wet type clutch facing, insulating paper and the like, and gives a product which can be easily handled and has excellent mechanical characteristics, and to a process for producing the same.

Background Art

Aromatic polyamides such as poly(paraphenylene terephthalamide), poly(metaphenylene isophthalamide) and the like (referred to hereinafter as aramides in some cases) have been known to be useful for fiber, pulp, film and the like which are excellent in heat resist¬ ance, mechanical characteristics, electric character- istics and the like. In particular, aramide pulp obtained by fibrillating aramide fibers is useful as asbestos-substitutes. Processes for producing aramide pulp have here-tofore been proposed. As an example, Japanese Pat. Appln. Kokoku No. 59-603 discloses a process for produc¬ ing aramide pulp by forming a film-like material or a monofila ent from an optically anisotropic dope of para- aromatic polyamide and then fibrillating the film-like material or monofilament by a mechanical shear force.

Japanese Pat. Appln. Kokai No. 2-200,809 discloses a process for producing aramide pulp directly from a solution of a polymer of a meta-aromatic poly¬ amide, and apparatus to be used therein.

When aramide fibers are to be used as rein¬ forcing fibers, it is important that the aramide fibers are excellent in wettability and adhesiveness to a resin or rubber which is a matrix, and hence, various methods have been proposed for the purpose of improving the wettability and adhesiveness between aramide fiber and matrix.

Japanese Pat. Appln. Kokai No. 62-218,425, for example, discloses a method of improving the adhesive¬ ness between an aramide fiber and an epoxy resin by immersing or spray-coating an aramide material (short fiber, long fiber, woven fabric, sheet or the like) in or with an organic solvent solution of an epoxy resin and also subjecting the same to heat-treatment to apply the epoxy resin to the surface of the aramide material. In addition, Japanese Pat. Appln. Kokai No. 62-225,539 discloses a method of improving the adhesiveness of an aramide material to an epoxy resin by heat-treating the aramide material in the presence of an ammonia gas before applying an epoxy resin to the aramide material. However, all these methods are concerned with treatment of aramide fibers having a fiber diameter of about 12 μm, and when these methods are applied to highly fibrillated aramide pulp having a fiber diameter of 1 μm or less the fibrils are adhered to one another to impair the dispersibility in water and fiber- separability of the aramide pulp, so that it is diffi¬ cult to apply the above methods as they are to the aramide pulp.

Moreover, in the case of producing a wet type clutch facing and the like, aramide pulp and other components such as inorganic filler are subjected to paper-making to prepare a composite paper; however, it is necessary in this case that fillers are uniformly dispersed in the paper. However, this is difficult because of a specific weight difference, and hence, it is intended to achieve the uniform dispersion by applying a dispersing aid or the like. However, at present, a satisfactory result is not always obtained, and the development of aramide pulp having so good a filler retaining property as to make the uniform dispersion possible has been desired.

Disclosure of the Invention

An object of this invention is to provide a water-containing aramide pulp which is applied to uses requiring a step of dispersing pulp in water to make paper as in the production of wet type clutch facing, insulating paper and the like and which is suitable for producing a product which is excellent in wettability and adhesiveness to a matrix and also in inorganic filler retaining property and exhibits high mechanical properties without impairing the dispersibility in water and fiber-separability of the aramide pulp. Another object of this invention is to provide a process for producing a water-containing aromatic polyamide which does not cause any environmental pollu¬ tion problems resulting from waste water and the like in the treatment of aramide pulp because the epoxy resin is 100% adsorbed on the pulp.

Other objects and advantages of this invention will become apparent from the following description.

According to this invention, there is provided a water-containing aromatic polyamide pulp which has been surface-treated with an epoxy resin and has a water content of 30 to 95% by weight.

This invention further provides a process for producing the above-mentioned water-containing aromatic polyamide pulp which comprises dispersing an aromatic polyamide pulp in an aqueous epoxy resin emulsion, filtering the resulting dispersion and dehydrating the pulp separated. Best Mode for Carrying out the Invention

The aramide used in this invention, that is, the wholly aromatic polyamide, is such that 85 mole % or more of the amide bonds are obtained from an aromatic ring diamine and aromatic ring dicarboxylic acid compo¬ nents.

Specific examples thereof include poly(para- phenylene terephthalamide), poly(metaphenylene tere¬ phthalamide) , polyparabenzamide, poly(4,4'-diamino- benzanilide) , poly(ρaraphenylene-2,6-naphthalene- dicarboxamide) , copoly(paraphenylene/4,4'-(3,3'- di ethyl-biphenylene) terephthalamide), copoly(para- phenylene/2,5-pyridylene terephthalamide), poly(ortho- phenylene phthal-amide) , poly(metaphenylene phthal- amide), poly(parapheny-lene phthalamide) , poly(ortho- phenylene isophthalamide), poly(metaphenylene isophthalamide), poly(paraphenylene isophthalamide), poly(orthophenylene terephthalamide), poly(l,5- naphthalene phthalamide) , poly(4,4'-diphenylene orthophthalamide) , poly(4,4'-diphenylene isophthal¬ amide), poly(l,4-naphthalene phthalamide), poly(l,4- naphthalene isophthalamide), poly(l,5-naphthalene isophthalamide) and the like; aromatic polyamides containing alicyclic amine, representatives of which are the above-mentioned aromatic diamines whose benzene nucleus has been partially replaced with piperazine, 1,5-dimethylpiperazine or 2,5-diethylenepiperazine; copolymers of aromatic polyamide containing two phenyl groups in which the aromatic diamines are bonded through an ether linkage such as 3,3'-oxydiphenylenediamine, 3,4'-oxydiphenylenediamine or the like, or a group such as -S-, -S0₂-, -CO-, -NH- or the like, for example, poly(3,3'-oxydiphenylene tere-phthalamide)/poly(para- phenylene terephthalamide) copolymer, poly(3,4- oxydiphenylene terephthalamide)/poly(paraphenylene terephthalamide) copolymer; and the like.

The term "aramide pulp" used herein means that having the form that aramide fibers are highly fibril¬ lated, whose specific surface area as measured by the BET method is preferably 3 to 25 m²/g, and whose free- ness as measured by the Canadian standard method in the "Pulp Freeness Test Method" of JIS P 8121 is preferably 100 to 700 ml, more preferably 150 to 700 ml.

The process for producing the aramide pulp is not critical and such processes as mentioned above can be applied.

The epoxy resin for preparing the aqueous epoxy resin emulsion used in this invention may be any epoxy resin as far as it can achieve the purpose of this invention, and the following can be used:

Bisphenol A type liquid epoxy resins such as Sumiepoxy ELA-128 (trade name of Sumitomo Chemical Co., Ltd.) and the like; bisphenol A type solid epoxy resins such as Sumiepoxy ELA-012 (trade name of Sumitomo Chemical Co., Ltd.) and the like; orthocresol novolak type epoxy resins such as Sumiepoxy ESCN-220L (trade name of Sumitomo Chemical Co., Ltd.) and the like; triglyci-dylamine type epoxy resins such as Sumiepoxy ELM-120 (trade name of Sumitomo Chemical Co., Ltd.) and the like; tetraglycidylamine type epoxy resins such as Sumiepoxy ELM-434 (trade name of Sumitomo Chemical Co., Ltd.) and the like; etc.

Among them, the tetrafunctional tetraglycidyl¬ amine type epoxy resin is preferred in view of enhancing adhesiveness. Furthermore, the epoxy equivalent of the epoxy resin is preferably 1,000 g/eq. or less.^{^} When it exceeds 1,000 g/eq. a sufficient adhesiveness cannot be obtained.

The production of an aqueous emulsion using the above epoxy resin can be effected by a conventional method. That is, an aqueous epoxy resin emulsion is obtained by dispersing an epoxy resin in water by a high speed stirring in the presence of a nonionic surface active agent such as an ether compound of polyoxy- ethylene and a higher fatty acid alcohol. In this case, the epoxy resin/surface active agent composition ratio by weight may be varied depend¬ ing upon the kind of epoxy resin and the kind of surface active agent. However, in view of the stability and adhesiveness of emulsion, the composition ratio is preferably in the range of 97/3 to 70/30. It is also possible to use commercially available epoxy emulsions which are those of epoxy resins such as ANS-1001, ANS- 1006 (trade names of Takemoto Yushi K. K.), KP-756, KP- 1011 (trade names of Matsumoto Yushi K. K. ) and the like. In view of uniformity of treatment, the particle size of emulsion is preferably 15 μm or less, more preferably 5 μm or less. A water-containing aromatic polyamide pulp excellent in adhesiveness to a phenol resin or the like can be prepared by treating aramide pulp with the above epoxy resin emulsion. In order to increase the amount of the epoxy resin adsorbed on the pulp in the treating solution, it is particularly preferable to hydrolyze a part of the glycidyl groups of the epoxy resin of the epoxy resin emulsion to convert the same to glycol groups, and no other particular means is required because the epoxy resin is 100% adsorbed on the aramide pulp.

The emulsion of the epoxy resin, the glycidyl groups of which have been partially hydrolyzed to glycol groups, can be produced by a method of preparing an emulsion using as the starting material the hydrolysis product of an epoxy resin by a generally known method.

It is also possible to use a method comprising preparing an epoxy resin emulsion by a conventional method as discussed below and then hydrolyzing the resulting emulsion. According to the latter method, a uniform, stable emulsion can be obtained easily. In order to hydrolyze the emulsion, various methods can be used depending upon the kind of the emulsion and it is the simplest to subject the emulsion as such to heat- treatment. When the emulsion is allowed to stand at about room temperature for about 3-6 months it has been confirmed that hydrolysis proceeds considerably, from which it is understood that the effect of this invention is substantially obtained by such a method. As a result of hydrolysis, a part of the epoxy groups of the epoxy resin is split to a glycol group. The conversion of the hydrolysis is preferably 10% or more, more preferably 20% or more and less than 90% of the initially existing epoxy groups. ^"""

When the hydrolysis is insufficient, the adsorption of the resin on the pulp tends to become insufficient, and when the hydrolysis is excessive, the performance of the treated pulp such as adhesiveness of the pulp to phenol resin or the like is reduced. In the hydrolysis, not only the formation of glycol groups but also increase of the molecular weight of the epoxy resin due to condensation are caused; however, as far as it does not adversely affect the stability of the emulsion it has no particular problem in this invention. The conversion of hydrolysis can be calculated from the following equation by measuring the epoxy equivalent:

Conversion (%) = 100 x {1 -(WPEi/WPEx)}

wherein WPEi is the initial epoxy equivalent and WPEx is the epoxy equivalent after the hydrolysis.

It has been found that by effecting the hydrolysis treatment, the zeta potential value which indicates the state of static electrification of epoxy resin particles in water is changed from strong negative value to strong positive value including polarity. The reason therefor is not necessarily clear; however, it is known that the zeta potential value of the aramide pulp shows a strong negative value, and hence, this elec¬ trical attraction is deemed to be a factor of the epoxy resin being substantially 100 % adsorbed on the pulp in the process of this invention.

The suitable hydrolysis conditions may be varied depending upon the epoxy resin used, the kind of surface active agent used, the proportions and concent¬ rations thereof and the like. As an example thereof, a nonionic emulsion [ANS-1006 (manufactured by Takemoto Yushi K. K.)] of Sumiepoxy ELM-434 (trade name of Sumitomo Chemical Co., Ltd.) which is a tetraglycidyl- amine type epoxy resin can be hydrolyzed in the follow¬ ing manner: The emulsion is heat-treated at 65°C for 130 hours to hydrolyze a part of the aiming glycidyl groups into glycol groups. By this treatment, the epoxy equivalent is increased from about 120 g/eq. to about 240 g/eq. In this case, the conversion of hydrolysis is about 50%. The zeta potential is changed from -20 mV to +15 mV. Also, as stated above, a similar effect can be obtained by allowing the epoxy resin emulsion to stand at room temperature for 3-6 months. Moreover, a catalyst such as an acid, an alkali, an amine or the like can be used to promote the reaction.

The treatment of aramide pulp with the above- mentioned epoxy resin emulsion, the glycidyl groups of which have been partially hydrolyzed, is effected, for example, by the following method: First of all, the aramide pulp is dispersed in water to the extent that a sufficient fluidity is obtained. The concentration of the aramide pulp dispersed in the dispersion is varied depending upon the specific surface area and the free- ness of the pulp, and is preferably in the range of 0.5 to 5% by weight. In order to uniformly disperse the pulp, a conventional propeller type stirrer can be used. A pulper for pulp which is used for dispersing usual linter pulp is particularly effective for achieving the uniform dispersion.

Subsequently, with stirring the dispersion, the desired amount of the above-mentioned epoxy emul¬ sion, the glycidyl groups of which have been partially hydrolyzed, is dropwise added. The amount of the emulsion added is such that the amount of the epoxy resin adhered is preferably 0.3 to 10% by weight, more preferably 0.5 to 10% by weight, most preferably 1 to 6% by weight, based on the weight of the dry pulp. When the amount of the epoxy resin adhered is less than 0.3% by weight, the desired mechanical properties are not obtained and a sufficient epoxy resin treating effect is not obtained. When it is more than 10% by weight, there is a tendency of the dispersibility of the pulp becoming bad, and an effect corresponding to the amount of the resin adhered is not obtained, so that it is inferior in economy.

After completion of the dropwise addition of the emulsion, the stirring as such is continued for 5 to 60 minutes to adsorb the epoxy resin on the pulp sur¬ face. According to the process of this invention, the epoxy resin is substantially 100% adsorbed on the aramide pulp surface only by the above treatment. The aramide pulp treated with the epoxy resin emulsion can also be heat-treated. The treated pulp subjected to heat-treatment shows a tendency that the increase of freeness due to the emulsion treatment is smaller than that of the pulp on which the same amount of epoxy resin has been merely adsorbed at room temper¬ ature. This means that the dispersibility of pulp is not impaired by the heat-treatment, which is a particu¬ larly desirable feature.

After the adsorption of the emulsion, the dispersion is filtered in a conventional manner. When the pulp is treated with the epoxy emulsion, the gly¬ cidyl groups of which have been partially hydrolyzed, as in this invention, no epoxy resin is detected in the filtrate and the COD value of the filtrate can be controlled to a level of about 10 ppm.

Thereafter, dehydration is effected so that the desired water content is obtained to obtain a surface-treated, water-containing aramide pulp. The water content of the pulp is adjusted to 30 to 95% by weight.

The water content referred to above can be determined from the following equation:

Water content (%) = {(Wl - W2)/W1} x 100

wherein Wl is the weight of the pulp in the hydrous state, and W2 is the weight of the pulp after drying.

In order to obtain a water content of less than 30%, a particular operation such as a great pres- sure, heat-drying or the like is required, and hence, this is not economical and, in addition, impairs the dispersibility of the treated pulp. When the water content is more than 95% by weight, the water-containing pulp becomes heavy, and hence, the operability becomes bad. Also, it is not economical in the aspect of trans¬ portation and the like. In uses such as wet type clutch facing, paper type gasket, insulating paper and the like which are prepared through the step of paper-making in water, the above-mentioned water content range is particularly preferable in view of easy handling, dispersibility and economy.

This invention is explained in more detail below referring to Examples, which are merely by way of illustration and not by way of limitation. In the Examples, the evaluation of water-containing aramide pulp was conducted by the methods described below. [Method of evaluating water-containing aramide pulp] 1. Evaluation method 1

Evaluation using aramide pulp/phenol resin impregnated paper (1) Paper-making

Water-containing pulp of a weight correspond¬ ing to 6.25 g of pulp in terms of absolute dry weight was weighed and dispersed in one liter of water at 3,000 rpm for 3 minutes in a 2-liter standard pulper (manufac- tured by Kumagai Riki Kogyo K. K. ) . Subsequently, paper-making was conducted in a conventional manner using a 25-cm square shaped sheet machine (manufactured by Kumagai Riki Kogyo K. K. ) and a # 80-mesh wire net, and thereafter dried at 120°C for 2 hours to obtain an aramide paper 25 cm square having an areal weight of 100 g/m².

(2) Impregnation with phenol resin

Several sheets of a test piece having a size of 50 M x 100 mm were cut from the above aramide paper and weighed. Subsequently, a 22.5% methanol solution of a modified resole type phenol resin [PR-SCI-3 (trade name of Sumitomo Durez Co. Ltd.)] was prepared by dilution. The test pieces were uniformly impregnated with this solution so that the pulp/resin weight ratio became 44.5/56.5, and then, dried at 50°C for 20 minutes to prepare an impregnated prepreg.

(3) Press-molding Two sheets of the above prepreg were put one on the other, a spacer of 0.6 mm in thickness was placed and the resulting assembly was press-molded at 180°C and 6 kg/cm² for 10 minutes and then treated at 180°C for 2 hours in an oven to post-cure the resin. (4) Tensile test

The impregnated paper obtained by the above- mentioned method was measured for tensile strength under the following conditions: Test piece size: 10 mm x 100 mm

Gauge length: 50 mm Crosshead speed: 5 mm/min 2. Evaluation method 2

Evaluation using aramide pulp/inorganic filler/ phenol resin clutch facing model molded article (1) Paper-making

Water-containing pulp of a weight correspond¬ ing to 6.25 g of pulp in terms of absolute dry weight and 4.2 g to 8.0 g of diatomaceous earth (controlled so that the pulp/diatomaceous earth weight ratio after paper-making became 6/4 depending upon the filler retaining property of pulp) were weighed, and then dispersed in one liter of water at 3,000 rpm for 3 minutes in a 2-liter standard pulper (manufactured by Kumagai Riki Kogyo K. K. ) . Subsequently, the dispersion was subjected to paper-making in a conventional manner in a square shaped sheet machine 25 cm square (manufac¬ tured by Kumagai Riki Kogyo K. K. ) using a # 80-mesh wire net, and thereafter dried at 120°C for 2 hours to obtain a 25-cm square aramide/diatomaceous earth composite paper (aramide/diatomaceous earth weight ratio: about 60/40) having an areal weight of about 167 g/cm².

(2) Diatomaceous earth (filler)-retention

The diatomaceous earth-retention of the treated pulp was determined from the following equation: Diatomaceous earth retention (%) = {(W3 - Wl)/W2} x 100 wherein Wl (g): Absolute dry weight of pulp (including the amount of treating agent adhered) W2 (g) : Weight of diatomaceous earth charged W3 (g): Dry weight of aramide/diatomaceous earth composite paper

(3) Impregnation with phenol resin

Several sheets of a sample of a size of 50 mm x 100 mm were cut from the above aramide paper and weighed. Subsequently, a 11.25% methanol solution of a modified resole type phenol resin [PR-SCI-3 (trade name of Sumitomo Durez Co., Ltd.)] was prepared by dilution. The above paper sample sheets were uniformly impregnated with this resin solution so that the pulp/diatomaceous earth/resin weight ratio became 60/40/35, and then dried at 50°C for 20 minutes to prepare an impregnated prepreg.

(4) Press-molding Two sheets of the above prepreg were put one on the other, a spacer of 0.6 mm in thickness was placed and the resulting assembly was press-molded at 180°C and 6 kg/cm² for 10 minutes, and thereafter treated in an oven at 180°C for 2 hours to post-cure the resin, thereby obtaining a clutch facing model molded article having a porosity of 50%. (5) Tensile test

The tensile strength of the molded article obtained by the above method was measured under the following conditions:

Test piece size: 10 mm x 100 mm Gauge length: 50 mm Crosshead speed: 5 mm/min 3. Evaluation method 3 (measurement of freeness)

The freeness of water-containing aramide pulp was measured according to the Canadian standard method in the "Pulp Freeness Test Method" of JIS P 8121. 4. Evaluation method 4 (Measurement of epoxy resin content)

The epoxy resin content (amount of resin adhered) of the water-containing aramide pulp was determined by calculation from the weight of the dry pulp obtained by extracting the epoxy resin adhered to pulp with dichloromethane by a Soxhlet extractor, and the weight of the extract. Example 1

At 80°C, 15 g of Sumiepoxy ELM-434 (trade name of Sumitomo Chemical Co., Ltd.), 1.5 g of Leodol SP-010 (trade name of Kao K. K. for a nonionic surface active agent) and 3.5 g of Leodol TW-L120 (trade name of Kao K. K. for a nonionic surface active agent) were stirred for 10 minutes to obtain a mixture. This mixture was cooled to room temperature, and then 80 cc of deionized water was dropwise added in one minute while the mixture was stirred at a high speed by a homogenizer, after which the stirring was continued for 3 minutes to obtain a stable epoxy resin emulsion. The particle size of the emulsion as measured by an optical microscope was 1 to 10 μm. In one liter of deionized water was dispersed

20 g of poly(paraphenylene terephthalamide) pulp [Towaron 1097 (trade name of Nippon Aramide Yugen Kaisha); speci-fic surface area by the BET method: 6.5 m²/g; water content: 6% by weight] in a flask. To the resulting dispersion was dropwise added 6.7 g of the above emulsion while the dispersion was stirred, and thereafter, the stirring was continued at room temper¬ ature for 30 minutes. Subsequently, the dispersion was filtered and the pulp separated was dehydrated so that the water content became about 70% by weight to obtain a water-containing aramide pulp which had been surface- treated with an epoxy resin. The performance of this water-containing aramide pulp was evaluated by the above-mentioned methods to obtain the results shown in Table 1. The dispersibility in water and fiber- separability of the water-containing aramide pulp were good.

Example 2

The same procedure as in Example 1 was repeat¬ ed, except that 4 g of Emulgen B-66 (trade name of Kao K. K. for a nonionic surface active agent) and 1 g of Kota-min B86P (trade name of Kao K. K. for a cationic surface active agent) were substituted for the surface active agent, to obtain an emulsion having a particle size of 0.5 to 3 μm. Furthermore, in the same manner as in Example 1, a water-containing pulp which had been surface-treated with an epoxy resin was obtained. This was evaluated in the same manner as in Example 1 to obtain the results shown in Table 1. The dispersibility in water and fiber-separability of the water-containing aramide pulp were good.

Example 3 The same procedure as in Example 1 was repeated, except that 5 g of Emulgen B-66 (trade name of Kao K. K. for a nonionic surface active agent) was substituted for the surface active agent, to obtain an emulsion having a particle size of 0.5 to 1 μm. More- over, a water-containing aramide pulp which had been surface-treated with an epoxy resin was obtained in the same manner as in Example 1. This was evaluated in the same manner as in Example 1 to obtain the results shown in Table 1. The dispersibility in water and fiber- separability of the water-containing aramide pulp were good.

Example 4

In one liter of deionized water was dispersed 20 g of Towaron 1097 in a flask. While the dispersion was stirred, 5.56 g of an epi-bis type epoxy emulsion [KP-756 (trade name of Matsumoto Yushi K. K.)] was dropwise added to the dispersion in one minute, after which the stirring was continued at room temperature for 30 minutes. Subsequently, the resulting mixture was filtered and the pulp separated was then dehydrated until the water content became about 70% by weight to obtain a water-containing aramide pulp which had been surface-treated with an epoxy resin. This pulp was evaluated in the same manner as in Example 1 to obtain the results shown in Table 1. The dispersibility in water and fiber-separability of the water-containing pulp were good.

Example 5

In one liter of deionized water was dispersed 20 g of Towaron 1097 in a flask, and with stirring this dispersion, 76.25 g of a polyglycidyl type epoxy emul¬ sion [ANS-1006 (trade name of Takemoto Yushi K. K. ) allowed to stand for 6 months at room temperature; epoxy equivalent: 271 g/eq.; conversion: 68%; zeta potential: +30 mV) ] was dropwise added to the dispersion in one minute, after which the stirring was continued at room temperature for 30 minutes. Subsequently, the resulting mixture was filtered, and the pulp separated was then dehydrated until the water content became about 70% by weight to obtain a water-containing aramide pulp which had been surface-treated with an epoxy resin. The performance of this pulp was evaluated in the above- mentioned evaluation method to obtain the results shown in Table 1. The dispersibility in water and fiber- separability of the water-containing aramide pulp were good.

Example 6

In one liter of deionized water was dispersed 20 g of Towaron 1097 in a flask, and with stirring this dispersion, 6.25 g of a polyglycidyl type epoxy emulsion [ANS-1006 (trade name of Takemoto Yushi K. K. ) was dropwise added to the dispersion in one minute, after which the stirring was continued at room temperature for 30 minutes. Thereafter, the temperature of the solution was elevated to 95°C and the stirring was continued for a further 2 hours. Subsequently, the resulting mixture was filtered and the pulp separated was then dehydrated until the water-content became about 70% by weight, to obtain a water-containing aramide pulp which had been surface-treated with an epoxy resin. The performance of this pulp was evaluated by the above-mentioned evalua¬ tion method to obtain the results shown in Table 1. The dispersibility in water and fiber-separability of this water-containing aramide pulp were good.

Example 7

In one liter of deionized water was dispersed 20 g of Towaron D1099 [trade name of Nippon Aramide Yugen Kaisha for poly(paraphenylene terephthalamide) pulp; specific surface area by the BET method: 16 m²/g; water content: 6% by weight] in a flask. With stirring this dispersion, 6.25 g of a polyglycidyl type epoxy emulsion [ANS-1006 (trade name of Takemoto Yushi K. K.); allowed to stand at room temperature for 6 months; epoxy equivalent: 371 g/eq.; conversion: 68%; zeta potential: +30 mV] was dropwise added to the dispersion in one minute, and the stirring was continued at room temper¬ ature for 30 minutes. Subsequently, the resulting mixture was filtered and the pulp separated was then dehydrated until the water content became about 70% to obtain a water-containing aramide pulp which had been surface-treated with an epoxy resin. This pulp was evaluated by the above-mentioned evaluation method to obtain the results shown in Table 1. The dispersibility in water and fiber-separability of this water-containing aramide pulp were good. Example 8

In a flask, 12 g of Towaron 1097 and 8 g of Towaron D1099 were dispersed in one liter of deionized water. In the same manner as in Example 7, a water- containing aramide pulp which had been surface-treated with an epoxy resin was obtained. Evaluation was effected in the same manner as in Example 7 to obtain the results shown in Table 1. The dispersibility in water and fiber-separability of this water-containing aramide pulp were good.

Comparative Example 1

Towaron 1097 (water content: about 6% by weight) was used without being subjected to treatment with an epoxy resin emulsion and evaluated by the above- mentioned evaluation method to obtain the results shown in Table 1.

Comparative Example 2

Towaron D1099 was used without being subjected to treatment with an epoxy resin emulsion and evaluated by the above-mentioned evaluation method to obtain the results shown in Table 1.

Comparative Example 3

A mixed pulp of 60 parts by weight of Towaron 1097 which had not been subjected to treatment with an epoxy resin emulsion and 40 parts by weight of Towaron D1099 which had not been subjected to treatment with an epoxy resin emulsion was used and evaluated by the above-mentioned evaluation method to obtain the results shown in Table 1.

Table 1

Example 9

In an oven, 2 kg of a polyglycidyl type epoxy emulsion [ANS-1006 (trade name of Takemoto Yushi K. K.)] was allowed to stand at 65°C for 130 hours to heat-treat the emulsion. The epoxy equivalent of the epoxy emulsion as measured by the hydrochloric acid-dioxane titration method was increased from 123 g/eq. to 238 g/eq. by this treatment. Therefore, the conversion of hydrolysis was 48%. Also, the zeta potential of the emulsion particles as measured by an ELS-800 electro- phoretic light-scattering photometer was changed from -20 mV to +15 mV. No change in appearance such as settlement of particles or the like was found.

Example 10 In one liter of deionized water was dispersed

10 g of Towaron D1099 [trade name of Nippon Aramide Yugen Kaisha for a poly(paraphenylene terephthalamide) pulp; specific surface area by the BET method: 16 m²/g; water content: 6% by weight] in a flask. With stirring this dispersion, 3.125 g of the epoxy emulsion prepared in the same manner as in Example 9 was dropwise added to the dispersion in 30 seconds, and the stirring was continued at room temperature for 30 minutes. Subsequ¬ ently, the resulting mixture was filtered and the pulp separated was then dehydrated until the water content became about 70% by weight to obtain a water-containing aramide pulp which had been surface-treated with an epoxy resin, the glycidyl group of which had been partially hydrolyzed. The performance of the water- containing aramide pulp was evaluated by the above- mentioned evaluation method to obtain the results shown in Table 2. The dispersibility in water and fiber- separability of the water-containing aramide pulp were good.

Example 11

In 150 liters of deionized water was^~~dispersed 1.4 kg of Towaron D1099 in a 200-liter reactor. With stirring this dispersion, 440 g of an epoxy emulsion prepared in the same manner as in Example 9 was dropwise added to the dispersion in two minutes, and the stirring was continued at room temperature for 30 minutes. Sub- sequently, the resulting mixture was filtered and the pulp separated was then dehydrated until the water content became about 70% by weight to obtain a water- containing aramide pulp which had been surface-treated with an epoxy resin, the glycidyl groups of which had been partially hydrolyzed. The performance of the pulp was evaluated by the above-mentioned method to obtain the results shown in Table 2. The dispersibility in water and fiber-separability of the water-containing pulp were good. Also, the amount of the epoxy resin in the filtrate after filtration was measured by the GPC analysis using a 254 nm ultraviolet ray detector in a 150-C type GPC analyzer manufactured by Waters in which the separating columns were Shodex KF 803, KF 802 and KF 801 (in series, each has a diameter of 8 mm and a length of 300 mm) manufactured by Showa Denko K. K.; however, no epoxy resin was detected in the filtrate. Moreover, according to the 100°C potassium permanganate method described in JIS K 0102.17, the COD of the filtrate after the dehydration was measured to obtain a value of 10 mg/liter.

Example 12 In one liter of deionized water was dispersed

10 g of Towaron D1099 in a flask, and with stirring this dispersion, 3.125 g of an epoxy emulsion (ANS-1006; conversion: substantially 0%) was dropwise added thereto in 30 seconds, after which the resulting mixture was stirred at room temperature for 30 minutes. Subsequ¬ ently, the mixture was filtered and the pulp separated was then dehydrated until the water content became about 70% by weight to obtain a water-containing aramide pulp which had been surface-treated with an epoxy resin. The performance of this pulp was evaluated by the above- mentioned evaluation method to obtain the results shown in Table 2. Moreover, in the same manner as in Example 11, the epoxy resin content and COD in the filtrate after the above filtration were measured to obtain values of 53 ppm and 110 mg/liter, respectively. Comparative Example 4

An aramide pulp (Towaron D1099; water content: about 6% by weight) which have not been subjected to any surface treatment was used as such in place of the surface-treated water-containing aramide pulp and evalu¬ ated by the above-mentioned evaluation method to obtain the results shown in Table 2.

Table 2

Industrial Applicability

The water-containing aromatic polyamide pulp of this invention is good in dispersibility in water and fiber-separability in the paper-making step, and has a suitable freeness, and also excellent in retention of an inorganic filler such as diatomaceous earth or the like. The pulp of this invention is also excellent in wetta¬ bility and adhesiveness to a matrix resin such as phenol resin or the like, and hence, can be used in the production of a impregnated paper and a molded article which are homogeneous and have excellent mechanical strength.

In the process of this invention, when there is used an emulsion of epoxy resin, the glycidyl group of which have been partially hydrolyzed, there is caused substantially no environmental pollution due to waste water even if no treatment of waste water is effected in the treatment of the pulp.

The water-containing aromatic polyamide pulp of this invention can be particularly effectively utilized in uses requiring a step of dispersing pulp in water to make paper such as wet type clutch facing, insulating paper and the like.

Claims

CLAIMS: 1. A water-containing aromatic polyamide pulp which has been surface-treated with an epoxy resin and has a water content of 30 to 95% by weight.
2. The water-containing aromatic polyamide pulp according to Claim 1, wherein the epoxy resin is an epoxy resin, the glycidyl groups of which have been partially hydrolyzed.
3. A process for producing a water-containing aromatic polyamide pulp as defined in Claim 1, which comprises dispersing an aromatic polyamide pulp in an aqueous epoxy resin emulsion, filtering the dispersion and dehydrating the pulp separated.
4. The process according to Claim 3, wherein the aqueous epoxy resin emulsion is an aqueous emulsion of an epoxy resin, the glycidyl groups of which have been partially hydrolyzed.