JPH07331581A - Aromatic polyester pulp-state material and its production - Google Patents

Abstract

PURPOSE:To produce a pulp-state material composed of a specified aromatic polyester and excellent in heat resistance and chemical resistance by treating a sea-island type fiber composed of specified components with a strongly alkaline solution and dissolving a pollester component ready in weight reduction by alkali. CONSTITUTION:A sea-island type fiber composed of a polyester ready in weight reduction as the sea component and an aromatic polyester having anisotropic melting properties as the island component is used and treated with a strongly alkaline solution (sodium hydroxide, etc.) to dissolve and/or decompose and remove the polyester ready in alkali weight reduction after or before the fiber is cut to <=5mm length. A pulp-state material composed of the aromatic polyester exhibiting anisotropic melting properties and having 0.5 to 5mm fiber length and 0.1 to 10mum diameter and free from a branch can be obtained thereby. This pulp-state material is excellent in nonhygroscopicity and has a high tenacity and a high modulus. It is, therefore, useful preferably for brake lining, clutch facing, etc. The polyester ready in weight reduction is preferably a polyester synthesized from a dicarboxylic acid, a diol, a hydroxy dicarboxylic acid, etc., and having >=3000 ratio of the alkali decomposition rate to that of the other aromatic polyester.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulp-like material composed of a melt anisotropic aromatic polyester and a method for producing the same.

[0002]

2. Description of the Related Art As a method for producing a pulp-like material made of an aromatic polyester, a method of melt-molding and then applying a shearing force to fibrillate it (Japanese Patent Laid-Open No. 201518/1989)
A mixture of an aromatic polyester and an easily soluble alkali-soluble organic compound is alkali-treated to remove the organic compound,
A method for beating the obtained hollow pulp-like material (JP-A-56)
-315) was known.

[Problems to be Solved by the Invention]

Since melt-anisotropic polyester fiber is highly molecularly oriented, it becomes relatively easily fibrillar when shearing force is applied. However, problems such as sticking and fusing occur together with the formation of pulp-like matter. It was difficult to manufacture. Furthermore, since the strength of the fiber is high, not only a great amount of time and labor are required for beating, but it is also difficult to obtain a pulp excellent in paper-making property and strength. Although beating must be repeated in order to obtain a pulp that can be made into paper, it is difficult to completely remove a pulp having a large diameter, and a powdery pulp is produced. Therefore, it was difficult to obtain a high paper strength because there was little entanglement of pulp pulps, and it was not possible to obtain a paper with excellent texture. Further, it is difficult to make a thin paper, and the powdery matter is clogged in the pipe at the time of paper making, and there is a problem in processability. The present invention is intended to solve the above problems and provide an excellent pulp-like material comprising a melt anisotropic polyester and a method for producing the same.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found an excellent pulp-like material and a method for producing the same. The present invention is an easy alkali weight-loss polyester (A polymer).
Is a sea component, and a sea-island fiber having a melt liquid crystalline aromatic polyester (B polymer) as an island component is cut before or after being cut to a length of 5 mm or less, and the alkali-reducible polyester (A polymer) is dissolved and It has been found that by decomposing and / or removing, a pulp-like material composed of a melt anisotropic aromatic polyester having a fiber length of 0.5 to 5 mm and a diameter of 0.1 to 10 μm and having substantially no branching is obtained. It is a thing. According to such a method, it is possible to produce a pulp-like material having a substantially uniform pulp length with little variation in diameter without applying shearing force to the melt-molded body. The pulp-like material of the present invention has substantially no branching (see FIG. 1), which is clearly different from the conventional pulp (see FIG. 2) obtained by beating a molded product. Since the pulp-like material of the present invention has substantially no branching, it has excellent dispersibility at the time of papermaking.

The easily loss-reducing polyester (A polymer) used in the present invention is a polyester composed of dicarboxylic acid, diol, hydroxycarboxylic acid and the like, and is a melt anisotropic aromatic polyester (B polymer) to be used. A polyester having an alkali decomposition rate ratio of 1000 times or more, and more preferably 3000 times or more is used. Therefore, since the alkali treatment can be carried out in a short time and the alkali resistance of the melt anisotropic aromatic polyester is excellent, the B polymer is not easily deteriorated or corroded by alkali, and a pulp-like material having excellent strength can be obtained. . Furthermore, since the A polymer can be almost completely removed by the treatment with the alkaline solution,
Trouble such as fusion does not occur in the next heat treatment process. It is possible to improve the heat resistance by adding a commercially available oxidative decomposition inhibitor (for example, Irganox 1010 manufactured by Ciba-Gaiki Co., Ltd., and Syanox 1790 manufactured by American Cyanamid Co., Ltd.) to the A polymer. . The alkali dissolution rate referred to in the present invention means that each measurement sample is placed in a 20 g / l sodium hydroxide aqueous solution at 98 ° C. at a bath ratio of 1:
The sample is dissolved under the condition of 500, and the sample is dissolved while stirring, and is represented by the alkaline rate constant K by the following formula.

[0006]

[Equation 1]

Suitable easy alkali weight-reducing polyester (A
Specific examples of the polymer) include the following structural units I to III.
Copolymerized polyesters containing are mentioned.

[0008]

[Chemical 1] (In the formula, Ar represents a trivalent aromatic group and M represents a metal)

[0009]

[Chemical 2] (In the formula, R ¹ is an alkylene group, m is an average degree of polymerization of 10 to 1
Indicates 00. )

[0010]

[Chemical 3] (In the formula, R ² represents an alkylene group, R ³ represents a hydrocarbon group having 1 to 18 carbon atoms, n represents an average degree of polymerization of 10 to 100, x
And y each represent 0 or 1.)

Particularly preferred is a polyester containing the structural units I to III, and the structural unit I is 0.5 to 10 mol% of all acid components constituting the polyester, the structural unit II and
Containing 1% by weight or more of each III, and structural units II and I
A copolyester having a total content of II of 2 to 50% by weight based on the whole polyester is used. The rate of alkali decomposition of the polyester is 1000 times or more as high as that of the aromatic polyester (B polymer), so that the treatment with the alkali solution can be performed in a short time. More preferably, a copolymerized polyester in which the structural unit I is 1 to 7 mol% of the total acid components constituting the polyester and the total content of the structural units II and III is 5 to 30% by weight of the total polyester is used.

When the content of the structural units I to III is small, the alkali decomposability may be insufficient. When the alkali decomposability is insufficient, it takes a long time to remove the A polymer, which causes a problem that the strength of the obtained pulp-like material is impaired. On the contrary, if the content of the copolymerization component increases, the spinnability may decrease. When the content ratio of the structural unit I is high, the viscosity becomes large and gelation is likely to occur. On the contrary, when the structural units II and III are increased, the viscosity is lowered and the yarn is easily broken. By copolymerizing the side chain unit III in an appropriate ratio, alkali decomposability and spinnability can be significantly improved.

Examples of the trivalent aromatic group (Ar) in the dicarboxylic acid unit I include a benzenetriyl group and a naphthalenetriyl group. The metal atom M is an alkali metal atom such as sodium, potassium or lithium. Is preferred.
The copolyester may have a plurality of dicarboxylic acid components I.

Other carboxylic acid units constituting the copolyester include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid and diphenyletherdicarboxylic acid,
Aromatic hydroxycarboxylic acids such as β-hydroxyethoxybenzoic acid and p-oxybenzoic acid, as well as aliphatic dicarboxylic acids, alicyclic carboxylic acids and tricarboxylic acids can be mentioned, and a plurality of these carboxylic acid units are used. May be. Of all the acid component units that make up the copolyester
It is preferable that 70 mol% or more is an aromatic dicarboxylic acid unit, particularly a terephthalic acid unit.

R ¹ in the diol unit II is preferably an alkylene group having 1 to 4 carbon atoms, ethylene group and / or propylene group, particularly ethylene group from the viewpoint of alkali solubility. . The average degree of polymerization m is 10
It is necessary to be -100, but 20-80 is more preferable. When m is less than 10, the alkali solubility is low, and when it exceeds 100, the alkali solubility is not improved so much, and a coloring problem is likely to occur. Units derived from polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene / polyoxypropylene glycol, etc. are preferred, and even if the copolymerized polyester contains a plurality of these diol units I. Good. Further, the copolyester preferably further has other diol units, and examples thereof include aliphatic diols and alicyclic diols. It may contain a plurality of these diol units. A unit derived from a linear alkylene glycol having 2 to 6 carbon atoms is preferable from the viewpoint of fiber forming property.

R ² in the side chain unit III is preferably an alkylene group having 1 to 4 carbon atoms, and is preferably an ethylene group and / or a propylene group, particularly an ethylene group. R ³ is a linear or branched alkyl group having 1 to 15 carbon atoms,
Examples thereof include a cycloalkyl group having 3 to 18 carbon atoms and an aryl group having 6 to 18 carbon atoms. The degree of polymerization n is 10 to 1
The range is 00, but 20 to 80 is more preferable. When n is less than 10, the alkali solubility decreases,
On the other hand, when it exceeds 100, the alkali solubility is not improved so much and causes coloring. Specifically, polyoxyethylene glycol-alkyl-glycidyl ether, polyoxyethylene glycol-alkyl-2,3-dihydroxypropyl ether, polyoxyethylene glycol-phenyl-glycidyl ether, Polyoxyethylene glycol-phenyl-2,3-dihydroxypropyl ether, polyoxyethylene glycol-cyclohexyl-glycidyl ether, polyoxyethylene glycol-cyclohexyl-2,3-dihydroxypropyl ether And the like, and a plurality of these units may be contained in the copolyester (A polymer).

The melt anisotropic aromatic polyester (B polymer) used in the present invention is a polymer obtained from, for example, an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, and the like. Examples of the polymer include polymers composed of a combination of repeating structural units shown in Chemical formulas 4 and 5. The B polymer used in the present invention has excellent alkali resistance and is suitable for use in the method for producing a pulp-like material of the present invention.

[0018]

[Chemical 4]

[0019]

[Chemical 5]

Particularly preferred is a melt anisotropic aromatic polyester in which the proportion of the constituent units of para-hydroxybenzoic acid (a) and 2-hydroxy6-naphthoic acid (b) is 80 mol% or more, and particularly a Aromatic polyesters in which the component b is 5 to 45 mol% with respect to the total amount of b and b are preferred. The melt anisotropy referred to in the present invention means an optical anisotropy in the melt phase. Such characteristics can be easily identified by a known method, for example, by heating a sample placed on a hot stage in a nitrogen atmosphere at elevated temperature and observing the transmitted light. The A polymer and / or B polymer used in the present invention may include titanium oxide, kaolin, silica, barium sulfate, carbon black, pigments, antioxidants, ultraviolet absorbers, light stabilizers, and the like. It may be included.

The kneading ratio of B polymer is based on all fibers.
10 to 60% by weight is preferred. The higher the ratio, the more economical and efficient, but if it exceeds 60% by weight, the B polymer becomes a sea component and the pulp-like material of the present invention cannot be obtained. The number of islands in the cross section of the sea-island fiber is about 40 to 1000, especially 70 to 300.
Individuals are preferred. The number of islands can be changed by adjusting the kneading ratio of A polymer and B polymer, spinning temperature, injection shear rate, draft, melt viscosity and the like.
For example, by increasing the difference in melt viscosity between both components,
The number of islands can be reduced. The sea-island fiber referred to in the present invention is not particularly limited as long as it is formed by extrusion and the island components are continuous to some extent in the fiber axis direction, such as diameter and cross-sectional shape. Specifically, a fibrous shape, a strand shape, a pellet and the like can be mentioned.

The pulp-like material of the present invention can be obtained by cutting it to a length of 5 mm or less, preferably 3 mm or less, more preferably 1-2 mm. The cutting may be carried out either before or after the alkali treatment, but it is preferable to carry out the cutting before the alkali reduction because the thicker the diameter, the easier the cutting. As a cutting method, any method such as a cutter, a pelletizer or a crusher may be used. If the cut length is too long, the pulp-like material is likely to be entangled after the alkali reduction and water dispersibility is deteriorated. On the other hand, if the cut length is too short, the entanglement between pulp-like materials is too small to obtain sufficient strength when processed into paper.

It is also possible to add a dispersant to the obtained pulp-like material. As the dispersant, polyether ester, C8 sulfosuccinate, polyoxyethylene (P
OE) nonylphenol ether sulphate amine, POE nonylphenol ether sulphate
Sodium, POE, nonylphenol, POE
Oleyl ether, a fluorine-based activator, a modified silicone and the like can be used. The dispersant is not limited to these, and a plurality of types may be used. Further, in order to improve the dispersibility of the pulp-like material, it is possible to reduce the entanglement between the pulp-like materials by applying a pulper, a refiner, a beater, etc. in a dry state, a wet state or a wet state in which a dispersant is added. It is possible.

Dissolution and / or decomposition and removal of the easily-alkaline weight-reducing polyester (A polymer) may be carried out by any method such as a dipping method, a dip nip method and a roller pad method. The alkaline solution used is preferably a strong alkaline solution such as sodium hydroxide, calcium hydroxide or trisodium phosphate, and is 2 to 60 g / l, more preferably 3 to 20 g from the viewpoint of alkali solubility and fiber erosion. Perform alkali treatment in a treatment solution of about 1 / l. sodium carbonate,
When a weakly alkaline substance such as sodium silicate or sodium dihydrogen phosphate is used, the concentration of the alkaline substance in the treatment liquid is 5 to 200 g / l, preferably 5 to 60 g / d. It is possible to use a strong alkaline substance and a weak alkaline substance together, and the treatment liquid may contain a decomposition accelerator and the like. Also, the addition of an alkaline surfactant is preferable because it promotes alkali penetration of the sea-island fiber.
The alkali treatment temperature is preferably 70 to 100 ° C. If the temperature is lower than 70 ° C, the time required for the temporary treatment becomes long, and if the temperature exceeds 100 ° C, not only the aromatic polyester (B polymer) is easily eroded and deteriorated, but also the autoclave. Equipment such as is required. After dividing the fibers by alkali treatment, it is preferable to carry out neutralization and water washing and drying treatment.

Since the melt-anisotropic aromatic polyester is easily oriented in the fiber axis direction, island components are likely to be continuous, and a relatively long pulp-like material can be obtained without cutting. Therefore, even if the cutting is carried out before or after the alkali reduction treatment, substantially no powdery matter is produced, and a pulpy matter having a substantially constant pulp length is obtained. When the powdery substance is mixed, not only the pipe is clogged and a big trouble is caused at the time of paper making, but also the strength of the obtained paper becomes low. In addition, as long as it does not impair the present invention, it may have a pulp-like material that does not have the shape specified in the present invention, but such a non-specified pulp-like material is 20% or less, preferably 10%. % Or less, and more preferably 5% or less. The aspect ratio (ratio of average diameter to length) of pulp is 500 to 150.
0, especially 800 to 1200 is preferable from the viewpoint of dispersibility and paper strength at the time of paper making.

The pulp-like material obtained according to the present invention may be used as it is, but it may be optionally heat-treated to further improve the performance such as strength and elastic modulus. The heat is supplied by a heating plate, an infrared heater or the like, a method of utilizing heat radiation, a heat roller, a method of contacting a plate or the like,
There is an internal heating method using high frequency. As the gas used as the heating medium, an inert gas such as nitrogen, a mixed gas of nitrogen and oxygen, carbon dioxide gas, or air is used. The heat treatment atmosphere has a dew point of -10 ° C or less, preferably -4
A gas at 0 ° C or lower is preferable. The preferable heat treatment condition is melting point T
m is a temperature pattern in which the temperature is gradually increased from Tm-40 ° C in the temperature range of Tm-60 ° C to Tm + 20 ° C.

The heat treatment may be performed under tension or without tension depending on the purpose. In addition, the shape is
It is carried out in the shape of a tease, tow (processed by placing it on a wire net), pellet or strand. A preferable heat treatment condition is a pattern in which the temperature is raised from Tm-40 ° C in the temperature range of Tm-60 ° C to Tm + 20 ° C with respect to the melting point Tm. The melting point referred to in the present invention means the temperature at which the maximum endothermic peak appears when the temperature of the sample is raised by a differential scanning calorimeter.

It is possible to make paper by a conventional method using only the pulp-like material obtained in the present invention, but it is possible to mix short-cut fibers composed of a polymer having the same composition as B polymer or a polymer having a different composition. Is also possible. In order to increase the strength of secondary products such as paper, it is preferable to use short cut fibers made of a melt anisotropic aromatic polyester, especially heat treated short cut fibers in combination. Further, it is possible to carry out a calendering treatment on the paper thus produced.

The pulp-like material obtained by the present invention is excellent in heat resistance, chemical resistance, non-hygroscopicity, etc., and has high strength and high elastic modulus, so that it can be used in various fields. Specifically, it can be processed into paper or the like and used for industrial materials and the like. For example, brake lining, clutch fade
Thing, bearings and other wear materials, packing materials, gasket materials, filters, abrasives, insulating paper, heat-resistant paper, speakers
Suitable for cones, wiping cloths, resin reinforcing agents, etc. In particular, it is excellent in non-hygroscopicity, chemical resistance, etc., and is suitable for the field of electrical insulation.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

【Example】

[Measurement of logarithmic viscosity] Pentafluorophenol sample
It was dissolved in 0.1% by weight (60 to 80 ° C.), and the relative viscosity (ηrel) was measured by a Uberode-type viscometer in a constant temperature bath at 60 ° C. and calculated by the following formula. ηinh = ln (ηrel) / c where c is the polymer concentration (g / dl). [Measurement of Intrinsic Viscosity] It was measured in an isothermal layer at 30 ° C. using an equal amount of a mixed solvent of phenol and tetrachloroethane. [Measurement of melting point] A sample of 5 to 15 mg is taken in a DSC (for example, TA3000 manufactured by Mettler), sealed in an aluminum pan, and nitrogen is passed at 20 cc / min. The melting point (Tm) is the peak temperature of the peak temperature.
To measure. If no clear endothermic peak appears in the 1st-run, the expected endothermic peak is raised at a temperature rise temperature of 50 ° C / min.
After melting for about 3 minutes at a temperature 50 ° C or more higher than the heating temperature and completely melting, cool it to 50 ° C at 80 ° C / min, then 20 ° C.
Use the value measured at a heating rate of / min. [Pulp diameter and pulp length] An electron micrograph of a pulp-like material is taken, and the diameter or pulp length is measured at arbitrary 10 points. Electron micrographs are taken at the other 5 arbitrary spots and similarly measured.

Example 1 Melt anisotropic polyarylate (B polymer) was prepared by adding parahydroxybenzoic acid and 2-hydroxy6-naphthoic acid to 73/2.
A 7 mol% ratio, a melting point (Tm) of 280 ° C., and an inherent viscosity of 5.7 dl / g were used. The easy alkali weight-reducing polyester (A polymer) is 2.5-sodium dimethyl sulfoisophthalate (I), which is 2.5% of all acid components constituting the copolyester.
Polyethylene glycol (I
I) and polyoxyethylene glycidyl ether (III) represented by Chemical formula 6 are 10% of all copolyesters, respectively.
It accounts for the weight% and the rest is terephthalic acid and ethylene glycol.
A copolymerized polyester (intrinsic viscosity of 0.58 dl / g), which is a polymer, was used. The alkali dissolution rate ratio of A polymer and B polymer was 5,800. The copolymerized polyester was 5% by weight of an antioxidant and an antioxidant (Asianox 179 manufactured by American Siamid Co., Ltd.) with respect to the total amount of the polyethylene glycol and polyoxyethylene glycidyl ether.
0) is included. The same copolymerization component and oxidative decomposition inhibitor were also used in Example 2 described later.

[0032]

[Chemical 6]

The above A polymer and B polymer are mixed at 50: 5.
It is melted and kneaded by an extruder at a weight ratio of 0, guided from a gear pump to a spinning head, head temperature 320 ℃, winding speed 300
m, draft 11 conditions, 1500d / 100f, 20 islands
0 sea island fibers were obtained. This was cut to a fiber length of about 1.5 mm using a cutter and then immersed in a boiling 40 g / l sodium hydroxide solution for 10 minutes. Next, this was transferred to a gauze, neutralized with acetic acid, and washed with water for 30 minutes to obtain a pulp-like material having an average diameter of about 1 μm (0.2 to 5 μm) and a fiber length of about 1.5 mm. Substantially no powdery substances or substances with extremely large fiber diameters were present.

Example 2 As a B polymer, structural units cf represented by the following chemical formula 7
A polymer having a molar ratio of c: d: e: f = 60: 20: 15: 5 (melting point 305 ° C., logarithmic viscosity 6.1 dl / g), head temperature 350 ° C., winding speed 600 / min, Spinning, cutting, and alkali treatment were performed in the same manner as in Example 1 except that the draft 20 was used. The alkali dissolution rate ratio of A polymer and B polymer was 3400. The obtained pulp-like material has an average diameter of about 0.7 μm (0.1 to 4 μm) and a fiber length of 1.5.
It was about mm.

[0035]

[Chemical 7]

Comparative Example 1 Shearing force was applied to the pellets of the molten liquid crystalline polyester (B polymer) used in Example 1 by using a refiner. It was difficult to obtain a pulp-like material by sticking the B polymer to the refiner's teeth and fibrillating them. A pulp-like material was obtained after further beating for a long time, but many large-diameter or powdery ones that do not fulfill the function as pulp due to uneven fiber diameters are included, and are suitable as pulp. Almost no one had a unique shape. Comparative Example 2 The molten liquid crystalline polyester used in Example 2 was used and beaten in the same manner as in Comparative Example 2. However, as in Comparative Example 1, sticking occurred and beating was difficult, and few pulp-like materials obtained had a shape suitable for pulp as in Comparative Example 1.

[0037]

Industrial Applicability According to the present invention, it becomes possible to efficiently produce an excellent pulp-like material made of a molten liquid crystalline polyester.

[Brief description of drawings]

FIG. 1 is a schematic view of a pulp-like material obtained by the present invention having substantially no branching.

FIG. 2 is a schematic diagram of a pulp-like material obtained by beating a molded product.

[Procedure amendment]

[Submission date] March 30, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019]

[Chemical 2]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location D01F 6/62 308 D21H 13/24 D06M 101: 32

Claims (2)

[Claims] 1. A fiber length of 0.5 to 5 mm and a diameter of 0.1.
A substantially branch-free pulp-like substance composed of a melt-anisotropic aromatic polyester having a thickness of 10 μm. 2. A sea-island fiber containing an easily alkali-reducing polyester (A polymer) as a sea component and a molten liquid crystalline aromatic polyester (B polymer) as an island component is cut before or after being cut to a length of 5 mm or less. A method for producing a substantially branchless pulp-like material comprising a molten liquid crystalline aromatic polyester, which comprises dissolving and / or decomposing and removing the easily alkali-reducing polyester (A polymer). [0001]