JP3301672B2 - Aromatic polyester pulp and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

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

[0002]

2. Description of the Related Art As a method for producing a pulp-like material composed of an aromatic polyester, a method of fibrillating by melt-molding and then applying a shearing force (Japanese Patent Application Laid-Open No. Hei 1-2201518).
And removing the organic compound by subjecting a mixture of an aromatic polyester and an alkali-soluble organic compound to an alkali treatment,
A method of beating the obtained hollow pulp-like material (JP-A-56
-315) was known.

[Problems to be solved by the invention]

[0003] Since the melt-anisotropic polyester fiber is highly molecularly oriented, it can be relatively easily fibril-shaped when shearing force is applied thereto. It was difficult to manufacture. Furthermore, since the strength of the fiber is high, not only a great amount of time and labor is required for beating, but also it is difficult to obtain a pulp excellent in papermaking property and strength. It is necessary to repeat beating in order to obtain a pulp that can be formed, but it is difficult to completely remove a pulp having a large diameter, and a pulp in the form of a powder is generated. Therefore, high pulp strength was hardly obtained due to little entanglement between the pulp, and furthermore, an excellent texture was not obtained. Further, it is difficult to make a thin paper, and the powdery material is clogged in the piping during the paper making, which causes a problem in processability. An object of the present invention is to solve the above problems and to provide an excellent pulp-like product made of a melt anisotropic polyester and a method for producing the same.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found an excellent pulp-like material and a method for producing the same. The present invention relates to an alkali-reducible polyester (A polymer)
Before or after cutting sea-island fibers having a sea component and a molten liquid crystalline aromatic polyester (B polymer) as an island component to a length of 5 mm or less, the alkali-reducible polyester (A polymer) is dissolved and dissolved. It has been found that a pulp-like substance having a fiber length of 0.5 to 5 mm and a diameter of 0.1 to 10 μm and having substantially no branch made of a melt anisotropic aromatic polyester can be obtained by decomposing and / or removing. It is a thing. According to such a method, it is possible to produce a pulp-like material having a small variation in diameter and a substantially uniform pulp length without applying a shearing force to the melt molded body. The pulp-like material of the present invention has substantially no branches (see FIG. 1), and is clearly different from the conventional pulp obtained by beating a molded product (see FIG. 2). Since the pulp-like material of the present invention has substantially no branch, it has excellent dispersibility at the time of paper making and the like.

The easily weight-reducing polyester (A polymer) used in the present invention is a polyester comprising dicarboxylic acid, diol, hydroxycarboxylic acid, etc., and a melt-anisotropic aromatic polyester (B polymer) used. A polyester having an alkali decomposition rate ratio of at least 1,000 times, more preferably at least 3000 times, is used. Therefore, the alkali treatment can be performed in a short time and the alkali anisotropy of the melt anisotropic aromatic polyester is excellent, so that the B polymer is hardly subject to deterioration or erosion by alkali, and a pulp-like material excellent in strength and the like can be obtained. . Further, since the A polymer can be almost completely removed by treatment with an alkaline solution,
No trouble such as fusion occurs in the next heat treatment step or the like. The heat resistance can also be improved by adding a commercially available antioxidant (for example, Irganox 1010 manufactured by Ciba-Gaiki, or Cyanox 1790 manufactured by American Cyanamid Inc.) to the A polymer. . In the present invention, the alkali dissolution rate is defined as the ratio of each sample in a 20 g / l aqueous solution of sodium hydroxide at 98 ° C. with a bath ratio of 1: 1.
The sample is immersed under the condition of 500, and the sample is dissolved with stirring.

[0006]

(Equation 1)

[0007] A preferred alkali-reducible polyester (A
Specific examples of the polymer) include the following structural units I to III
And the like.

[0008]

Embedded image (In the formula, Ar represents a trivalent aromatic group, and M represents a metal.)

[0009]

Embedded image (Wherein, R ¹ is an alkylene group, m is an average degree of polymerization of 10 to 1)
00 is shown. )

[0010]

Embedded image (Wherein, 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, wherein the structural unit I is 0.5 to 10 mol% of the total acid components constituting the polyester, the structural unit II and
III each containing 1% by weight or more, and the structural units II and I
A copolyester having a total content of II of 2 to 50% by weight of the total polyester is used. The alkali decomposition rate of the polyester is 1000 times or more larger than that of the aromatic polyester (B polymer), and therefore, the treatment with the alkali solution can be performed in a short time. More preferably, a copolymerized polyester is used 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.

When the content of the structural units I to III is small, the alkali decomposability may be insufficient. If the alkali decomposability is insufficient, it takes a long time to remove the A polymer, which causes problems such as impairing the strength of the obtained pulp-like material. Conversely, if the content of the copolymer component increases, the spinnability may decrease. If the content ratio of the structural unit I is high, the viscosity increases and gelation easily occurs. Conversely, if the structural units II and III increase, the viscosity decreases and the thread breakage and the like easily occur. By copolymerizing the side chain unit III at 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 copolymerized polyester may have a plurality of dicarboxylic acid components I.

Other carboxylic acid units constituting the copolymerized polyester 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, and further aliphatic dicarboxylic acids, alicyclic carboxylic acids, and tricarboxylic acids can be used, and a plurality of these carboxylic acid units can be used. You may. Of all the acid components constituting the copolymerized polyester
It is preferred that at least 70 mol% be aromatic dicarboxylic acid units, especially terephthalic acid units.

R ¹ in the diol unit II is preferably an alkylene group having 1 to 4 carbon atoms, and is preferably an ethylene group and / or a propylene group, particularly preferably an ethylene group from the viewpoint of alkali solubility. . The average degree of polymerization m is 10
１００100 is required, but 20-80 is more preferred. If m is less than 10, the alkali solubility is low, and if it exceeds 100, the alkali solubility is not so improved, and the problem of coloring is likely to occur. Units derived from polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene / polyoxypropylene glycol, and the like are preferable, and even if the copolymerized polyester contains a plurality of these diol units I, Good. The copolymerized polyester preferably further has another diol unit, and examples thereof include an aliphatic diol and an alicyclic diol. A plurality of these diol units may be included. A unit derived from a linear alkylene glycol having 2 to 6 carbon atoms is preferred from the viewpoint of fiber-forming properties.

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 preferably an ethylene group. R ³ represents 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
Although it is in the range of 00, it is more preferably in the range of 20 to 80. If n is less than 10, alkali solubility decreases,
On the other hand, if it exceeds 100, the alkali solubility does not improve 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 copolymerized polyester (A polymer).

The melt-anisotropic aromatic polyester (B polymer) used in the present invention is, for example, a polymer obtained from an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, or the like. Is a polymer comprising a combination of the 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 product of the present invention.

[0018]

Embedded image

[0019]

Embedded image

Particularly preferred is a melt-anisotropic aromatic polyester in which the portion composed of the constituent units of parahydroxybenzoic acid (a) and 2-hydroxy-6-naphthoic acid (b) is at least 80 mol%. Aromatic polyesters in which the b component is 5 to 45 mol% based on the total amount of b and b are preferred. The term “melt anisotropy” as used in the present invention indicates optical anisotropy in a molten phase. Such characteristics can be easily identified by a known method, for example, heating a sample placed on a hot stage under a nitrogen atmosphere and observing the transmitted light. The A polymer and / or B polymer used in the present invention may contain titanium oxide, kaolin, silica, barium sulfate, carbon black, pigment, antioxidant, ultraviolet absorber, light stabilizer, etc., as appropriate. May be included.

The kneading ratio of the B polymer is based on the total fiber.
10-60% 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 product of the present invention cannot be obtained. The number of islands in the cross section of sea-island fiber is about 40 to 1000, especially 70 to 300
Are preferred. The number of islands can be changed by adjusting the kneading ratio of the A polymer and the B polymer, spinning temperature, injection shear rate, draft, melt viscosity, and the like.
For example, by increasing the difference in melt viscosity between the two 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 component is continuous to some extent in the fiber axis direction. Specific examples include a fibrous shape, a strand shape, and a pellet.

The pulp-like material of the present invention is obtained by cutting to a length of 5 mm or less, preferably 3 mm or less, more preferably 1-2 mm. The cutting may be performed either before or after the alkali treatment, but it is preferable to cut before the alkali weight reduction because a larger diameter is easier to cut. As a cutting method, any method such as a cutter, a pelletizer, and a pulverizer may be used. If the cut length is too long, the pulp-like substance tends to be entangled after the alkali weight loss, and the water dispersibility deteriorates. Conversely, if the cut length is too short, the entanglement between the pulp-like materials is too small to obtain sufficient strength when processed into paper.

It is also possible to add a dispersant to the pulp obtained. Examples of the dispersant include polyetherester, C8 sulfosuccinate, polyoxyethylene (P
OE) nonylphenol ether sulfate amine, POE nonylphenol ether sulfate
Sodium, POE, nonylphenol, POE
Oleyl ether, fluorine-based activator, 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 enhance the dispersibility of the pulp-like material, it is also possible to reduce the entanglement between the pulp-like materials by applying it to a pulp, a refiner, a beater or the like in a dry state, a wet state or a wet state to which a dispersant is added. It is possible.

The dissolution and / or decomposition and removal of the alkali-reducible 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 to be used is preferably a strong alkaline solution such as sodium hydroxide, calcium hydroxide, trisodium phosphate, etc., from the viewpoint of alkali solubility and fiber erosion, 2 to 60 g / l, more preferably 3 to 20 g. Perform alkali treatment in a treatment solution of about / l. sodium carbonate,
When a weak 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. These can be used in combination with a strong alkali substance and a weak alkali substance, and the processing solution may contain a decomposition accelerator or the like. In addition, the addition of an alkali surfactant is preferable because alkali permeation of sea-island fibers is promoted.
The alkali treatment temperature is preferably from 70 to 100 ° C. When the temperature is lower than 70 ° C., the time required for the preliminary treatment becomes longer, and when the temperature is higher than 100 ° C., not only is the aromatic polyester (B polymer) susceptible to erosion and deterioration, but also the autoclave becomes harder. Equipment such as is required. After splitting the fibers by alkali treatment, it is preferable to carry out neutralization, washing with water and drying.

Since the melt-anisotropic aromatic polyester is easily oriented in the fiber axis direction, the island component tends to be continuous, and a relatively long pulp-like material can be obtained without cutting. Therefore, even if cutting is performed before or after the alkali weight reduction treatment, a powdery substance is not substantially generated, and a pulp-like substance having a substantially constant pulp length is obtained. In the case where a powdery substance is mixed, not only does the piping become clogged at the time of papermaking, but also the strength of the obtained paper is low. In addition, as long as it does not impair the present invention, it may have a pulp-like material not having the shape specified in the present invention. % Or less, more preferably 5% or less. The aspect ratio (ratio of average diameter to length) of the pulp is 500 to 150.
0, particularly 800 to 1200, is preferred in terms of dispersibility and paper strength during papermaking.

The pulp-like material obtained according to the present invention may be used as it is, but may optionally be subjected to a heat treatment to further improve properties such as strength and elastic modulus. The heat is supplied by a method using heat radiation by a heating plate, an infrared heater or the like, a method of contacting with a heat roller, a plate, or the like,
There is an internal heating method using high frequency or the like. As a gas used as the heating medium, an inert gas such as nitrogen, a mixed gas such as nitrogen and oxygen, a carbon dioxide gas, and air are used. The heat treatment atmosphere has a dew point of -10 ° C or less, preferably -4 ° C.
Good in gas below 0 ° C. Preferred heat treatment conditions are melting point T
m, a temperature pattern in which the temperature is gradually increased from Tm-40 ° C. in a 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. Also, the shape is squamous,
It is performed in the form of a tooth, a tow (processed on a wire net), a pellet, or a strand. A preferred heat treatment condition is a pattern in which the temperature is gradually increased from a temperature of Tm-40 ° C. within a temperature range of Tm−60 ° C. to Tm + 20 ° C. with respect to the melting point Tm. The melting point in the present invention refers to a temperature at which a maximum endothermic peak appears when a sample is heated by a differential scanning calorimeter.

It is possible to make a paper by a conventional method using only the pulp-like material obtained in the present invention, but it is necessary to mix short cut fibers comprising a polymer having the same composition as B polymer or a different composition. Is also possible. In order to increase the strength of a secondary product such as paper, it is preferable to use a short-cut fiber made of a melt-anisotropic aromatic polyester, particularly a heat-treated short-cut fiber. It is also possible to calender the paper made.

The pulp-like product obtained in the present invention has excellent heat resistance, chemical resistance, non-hygroscopicity and the like, and also has a high strength and a 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 material applications and the like. For example, brake lining, clutch
Wear materials such as sings and bearings, packing materials, gasket materials, filters, abrasives, insulating paper, heat-resistant paper, speakers
Suitable for cones, wiping cloths, resin reinforcing agents, and the like. Particularly, since it is excellent in non-hygroscopicity, chemical resistance and the like, it is suitable for the field of electric insulation.

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

【Example】

[Measurement of logarithmic viscosity] Sample was converted to pentafluorophenol
0.1 wt% was dissolved (60-80 ° C), and the relative viscosity (ηrel) was measured with a Ubbel-de-type viscometer in a thermostat at 60 ° C and calculated by the following equation. ηinh = ln (ηrel) / c where c is the polymer concentration (g / dl). [Measurement of Intrinsic Viscosity] The intrinsic viscosity was measured in a thermostat at 30 ° C. using a mixed solvent of equal amounts of phenol and tetrachloroethane. [Measurement of melting point] After taking 5 to 15 mg of a sample in a DSC (for example, TA3000 manufactured by Mettler), sealing the sample in an aluminum pan, flowing nitrogen at 20 cc / min, and measuring at a heating rate of 20 ° C./min, an endothermic The temperature representing the peak of the peak temperature is the melting point (Tm).
Measured as If a clear endothermic peak does not appear in the 1st-run, the expected endothermic peak is increased at 50 ° C / min.
After heating for about 3 minutes at a temperature 50 ° C or more higher than the cooling temperature to completely melt, cool 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 the pulp is taken, and the diameter or pulp length is measured at any 10 points. Electron micrographs are taken at five other arbitrary locations and measured in the same manner.

Example 1 A melt anisotropic polyarylate (B polymer) was prepared by mixing parahydroxybenzoic acid and 2-hydroxy6-naphthoic acid at 73/2.
Those having a 7 mol% ratio, a melting point (Tm) of 280 ° C. and an logarithmic viscosity of 5.7 dl / g were used. The alkali-reducible polyester (A polymer) is composed of dimethyl (I) 5-sodium sulfoisophthalate of 2.5% of all the acid components constituting the copolymerized polyester.
Mol%, polyethylene glycol having a molecular weight of 2000 (I
The polyoxyethylene glycidyl ether (III) represented by the formulas (I) and (6) was 10
Terephthalic acid, ethylene glycol
A copolyester (intrinsic viscosity 0.58 dl / g) was used. The alkali dissolution rate ratio between the A polymer and the B polymer was 5,800. The copolymerized polyester was an antioxidant of 5% by weight based on the total amount of the polyethylene glycol and the polyoxyethylene glycidyl ether (Cyanox 179 manufactured by American Cyamid Co., Ltd.).
0). The same copolymer component and antioxidant were used in Example 2 described later.

[0032]

Embedded image

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

Example 2 As the B polymer, the structural units cf shown in the following formula 7
Using 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 between the A polymer and the B polymer was 3,400. 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 μm.
mm.

[0035]

Embedded image

Comparative Example 1 The molten liquid crystalline polyester (B polymer) pellets used in Example 1 were subjected to a shearing force using a refiner. It was difficult to obtain a pulp-like product by agglomeration and fibrillation of the B polymer on the teeth of the refiner. Furthermore, pulp-like material was obtained after long-time beating treatment, but the fiber diameter was not uniform, and many pulp-like materials with large diameters and powders that did not sufficiently function as pulp were included, making it suitable as pulp. There was almost no thing having a perfect shape. Comparative Example 2 The melted liquid crystalline polyester used in Example 2 was beaten in the same manner as in Comparative Example 2. However, as in Comparative Example 1, sticking occurred and beating was difficult, and as in Comparative Example 1, there were few pulp-like products having a suitable shape as pulp.

[0037]

According to the present invention, it has become possible to efficiently produce an excellent pulp-like product comprising a molten liquid crystalline polyester.

[Brief description of the drawings]

FIG. 1 is a schematic view of a substantially unbranched pulp obtained according to the present invention.

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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI D06M 101: 32 D06M 5/02 F (58) Investigated field (Int.Cl. ⁷ , DB name) D06M 11/38 D01F 8 / 14 D01F 6/62 D21H 13/24

Claims (2)

(57) [Claims] 1. A fiber length of 0.5 to 5 mm and a diameter of 0.1
A substantially unbranched pulp-like material comprising a melt-anisotropic aromatic polyester having a size of from 10 to 10 µm. 2. A sea-island fiber having an alkali-reducible polyester (A polymer) as a sea component and a molten liquid crystalline aromatic polyester (B polymer) as an island component is cut or cut before cutting into a length of 5 mm or less. A method for producing a substantially non-branched pulp-like product comprising a molten liquid crystalline aromatic polyester, comprising dissolving and / or decomposing and removing the alkali-reducible polyester (A polymer). [0001]