JPH04141202A - Method for drying aqueous slurry containing crosslinked polymer particles - Google Patents

Abstract

PURPOSE:To dry an aqueous slurry containing crosslinked polymer to obtain particles excellent in dispersibility by drying the aqueous slurry containing the crosslinked polymer particles whose primary particle size is specific in specific wt.% in a spray dryer so as to bring the same to specific water content after drying. CONSTITUTION:Crosslinked polymer particles (mean particle size; 0.05-3mum) obtained as an aqueous slurry are sprayed to hot air in a mist form to evaporate water to obtain dried particles. As a method for spraying the aqueous slurry in a mist form, both of a disc type one dripping the aqueous slurry on a disc rotating at high speed as liquid droplets to form the same into mist and a nozzle type one simultaneously emitting high pressure air and the aqueous slurry from a small slit to form the aqueous slurry into mist may be used. The concn. of the particles in the aqueous slurry supplied to a spray dryer is 0.5-20wt.% and the aqueous slurry is dried so that the water content of the dried particles becomes 2-15wt.%. The crosslinked polymer particles obtained by this method have excellent dispersibility and are useful as the additive of polyester and have high industrial value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for drying crosslinked polymer particles added to polyester.

[Problem B to be solved by the prior art and the invention] Biaxially oriented films of polyesters, particularly polyethylene terephthalate, have excellent physical and chemical properties, and are useful as base films for magnetic recording media and dielectrics for capacitors. It is prized as a body. Furthermore, due to its excellent transparency, it is widely used in fields such as graphic arts, displays, and packaging materials. In recent years, there has been a marked trend toward higher quality films in each of these applications, and it has become strongly desirable for the film surface to be uniform and free from coarse protrusions.

It is generally known that in order to improve the running properties of a film, the surface of the film can be appropriately roughened.

In order to achieve this, some methods have been put into practical use in which organic particles, such as monodisperse crosslinked polymer particles, are present in the raw material polyester.

Generally, crosslinked polymer particles are obtained as an aqueous slurry by emulsion polymerization using an aqueous medium, so when adding the particles to polyester, it is necessary to remove water to form an ethylene glycol slurry.

Generally, methods for removing water include methods such as using an evaporator to remove water under reduced pressure and replacing it with ethylene glycol, or drying particles using a so-called spray dryer, but water removal using an evaporator is not efficient. Not only that, but heat is applied for a long time, which adversely affects the morphology and properties of the particles. When drying with a spray dryer, organic particles often fuse together due to the hot air treatment, making it difficult to disperse them in ethylene glycol.

Therefore, when organic particles obtained by drying a water slurry using conditions generally applied to inorganic particles are blended into a polyester film, coarse protrusions often appear on the film surface due to agglomeration of the particles. If such a film is used for magnetic recording, it will cause deterioration of electromagnetic exchange characteristics and frequent dropouts.

[Means to solve the problem]

In view of the above circumstances, the present inventors have conducted extensive studies and found that, when drying a water slurry containing crosslinked polymer particles, if drying is performed so that a certain amount of water remains in the particles, Excellent dispersibility in ethylene glycol,
It was discovered that extremely excellent properties could be obtained as particles for adding to polyester film, and the present invention was completed.
Ta.

That is, the gist of the present invention is that - the particle diameter is 0.05 to 3μ;
When drying an aqueous slurry containing 0.5 to 20% by weight of crosslinked polymer particles, which is m, in a spray dryer, drying is performed so that the moisture content of the particles after drying is 2 to 15% by weight. The present invention relates to a method for drying an aqueous slurry containing crosslinked polymer particles.

The present invention will be explained in more detail below.

The polyester blended with the crosslinked polymer particles of the present invention is:
It refers to a polyester obtained using an aromatic dicarboxylic acid such as terephthalic acid and 2,6-naphthalene dicarboxylic acid or its ester, and ethylene glycol as the main starting materials, but it may contain other third components.

As the dicarboxylic acid component, one or more of, for example, isophthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, and sebacic acid can be used. In addition, as glycol components, diethylene glycol, propylene glycol, butanediol, 1.4-
One or more of cyclohexane dimetatool and neopentyl glycol can be used. In any case, the polyester used in the present invention refers to a polyester in which 80% or more of the repeating structural units have ethylene terephthalate units or ethylene-2,6-naphthalate units. Further, a polyester film can be manufactured by orienting such polyester in at least one axis, and a known method can be used as the manufacturing method.

For example, it is usually melt-extruded into a sheet at 270-320°C, cooled and solidified at 40-80°C to form an amorphous sheet, and then heated at 80-130°C with an area magnification of 4 in the vertical and horizontal directions.
Sequential or two-wheel stretching so that it becomes ~20 times, 160 ~
A method of heat treatment at 250°C (for example, the method of heat treatment at 250°C
The method described in Publication No. 39) can be used. When stretching in the longitudinal and transverse directions, stretching may be carried out in each stage, or in multiple stages if necessary, or a heat treatment section for orientation relaxation may be provided between multi-stage stretching. . Further, after the two-wheel stretching, the film may be stretched again before being subjected to the next heat treatment step. This re-stretching can be performed in either the longitudinal or lateral direction, or in both directions.

The method for producing crosslinked polymer particles used in the present invention is not particularly limited, but a typical example is one or more monovinyl compounds (A) having only one aliphatic unsaturated bond in the molecule, and crosslinked polymer particles. A method may be mentioned in which one or more compounds (B) having two or more aliphatic unsaturated bonds in the molecule are used as the agent and a so-called emulsion polymerization method is applied.

The emulsion polymerization method herein refers to emulsion polymerization in a broad sense, including concepts such as soap-free emulsion polymerization and seed emulsion polymerization. The compounds (A) used to obtain monodisperse crosslinked polymer particles include acrylic acid, methacrylic acid, and alkyl or glycidyl esters thereof, maleic anhydride and alkyl derivatives thereof, vinyl glycidyl ether, vinyl acetate, styrene, and alkyl-substituted esters. Examples include styrene. Examples of the compound (B) include divinylbenzene, divinyl sulfone, and ethylene glycol dimethacrylate. Compound (A
) and (B) are used at least one type each, but a compound having a nitrogen atom or ethylene may be copolymerized.

The average particle size of the crosslinked polymer particles used in the present invention is 0, 0, which is usually used for adding polyester films.
It is in the range of 5 to 3 μm, preferably in the range of 0.1 to 1 μm.

In addition, if the average particle diameter of the particles is less than 0.05 μm, the running properties of the film containing such particles will be insufficient,
Moreover, if it exceeds 3 μm, the surface roughness of the film becomes too large, which is not preferable.

The ratio of the particle size (dis) when the cumulative weight of the crosslinked polymer used in the present invention is 25% from the large particle side to the particle size (dys) when the cumulative weight of the particles is 75% [d□/d
Tsl value is usually 167 or less, preferably 1.6
It is more preferably 1.5 or less. This value is 1
．． If it exceeds 7, it is not preferable because a uniform film surface cannot be obtained. Further, the particles may or may not be porous, but the former is preferred because it has better affinity with polyester.

A more specific embodiment of the production of crosslinked polymer particles in the present invention is as follows.

That is, after dissolving a predetermined amount of a water-soluble polymerization initiator such as hydrogen peroxide or potassium persulfate in a medium mainly composed of water, a mixed solution of a predetermined amount of compounds (A) and (B) is prepared. Add. Thereafter, the reaction is carried out for about 3 to 10 hours with stirring at a temperature higher than the decomposition start temperature of the polymerization initiator, preferably 30 to 90°C.

At this time, some aggregated particles may be formed depending on the composition of the 7-mer, so in this case it is preferable to add a dispersion stabilizer such as an emulsifier to maintain the dispersion stability of the particles.

In either case, the produced particles are obtained as a uniformly dispersed water slurry.

In the present invention, as a method for drying such water slurry, a method using a spray dryer generally called a spray dryer is adopted. In this method, a water slurry is atomized and the water is evaporated in hot air to obtain dry particles, but it is usually accompanied by a device that converts the particles into secondary aggregates and collects them with a cyclone. There is. There are two ways to make water slurry into a mist: the disk type, in which the water slurry is dropped as droplets onto a disk that rotates at high speed, and the water slurry is made into a mist by simultaneously releasing high-pressure air and water slurry through a small gap. There is a nozzle type that makes the water into a mist, but you can use either one.

In the present invention, the particle concentration of the water slurry fed to the spray dryer is from 0.5 to 20% by weight, preferably from 1 to 15% by weight. If this value is less than 0.5% by weight, thermal loss is large and it is not economical, and if it exceeds 20% by weight, drying often becomes uneven and fusion of particles occurs.

The most important feature of the present invention is that the particles dried by this method are dried so that the moisture content is 2 to 15% by weight, preferably 3 to 13% by weight, and more preferably 4 to 10% by weight. If the water content in the particles is less than 2% by weight, the surface of the crosslinked polymer particles will partially melt due to the hot air during drying with a spray dryer, and the particles will fuse together to form aggregates. Put it away. This aggregate becomes difficult or impossible to disperse in ethylene glycol. If the particles are dried so that the water content is less than 15% by weight, the dispersibility is good, but the particles tend to stick to the equipment, resulting in a poor yield, and the amount of water in the ethylene glycol is high. Therefore, when added to polyester, it causes bumping and particle aggregation, which is not preferable.

In the present invention, such particles containing an appropriate amount of moisture are collected in the form of secondary particles in which several primary particles are gently aggregated, and then subjected to a classification process to obtain particles of a desired particle size. is preferred.

When adding the crosslinked polymer particles obtained by the method of the present invention to a film, the blending amount is usually 0.01 to 4% by weight.
, preferably in the range of 0.05 to 0.8% by weight. If the amount is less than 0.01% by weight, the slipperiness of the film will be insufficient, and if it exceeds 4% by weight, the surface roughness of the film will become too large and the electromagnetic properties will deteriorate, which is not preferable.

Note that the method of blending the dry crosslinked polymer particles 1 obtained in the present invention with the polyester as a film forming raw material is carried out at any stage of the ester production process in which the sashiko is prepared as an ethylene glycol slurry dispersion, preferably esterification or esterification. It is preferable to add it after the completion of the exchange reaction and before the start of the polycondensation reaction to advance the polycondensation reaction. In this case, the concentration of the particles in the ethylene glycol slurry is usually selected from the range of 1 to 30% by weight. Further, as a method for dispersing the slurry, for example, in addition to ultrasonic dispersion treatment, a rod mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a roller mill, an impact mill, an agitation crushing mill, a fluid energy mill, etc. are used.

The polyester film containing the crosslinked polymer particles of the present invention takes advantage of its uniform surface free of coarse protrusions, and can be used as a base film for magnetic recording media such as magnetic tapes and floppy disks, as well as for capacitors and photolithography. It is extremely useful as a base film for various fields such as printing, thermal transfer, packaging, transfer marks, and gold and silver thread.

[Examples] Hereinafter, the present invention will be explained in more detail using Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, the measurement methods and definitions of various physical properties and characteristics in Examples are as follows. In Examples and Comparative Examples, "parts" indicate "parts by weight."

(1) Average particle size and particle size distribution Centrifugal sedimentation type particle size distribution analyzer (SA-C
The average particle size was defined as the particle size at an integrated weight fraction of 50% in the equioblate spherical distribution measured with Pa type. At the same time, when integrating from the large particle side, the ratio (d ts / d 75 ) of the particle size (dgs) when the cumulative weight of the particles is 25% and the particle size (dys) when the cumulative weight of the particles is 75% is the particle size distribution. The ratio was taken as the ratio of

(2) Moisture content in the particles The moisture content in the dry particles was determined using a moisture measuring device (Model CA-06 manufactured by Mitsubishi Kasei ■).

(3) Using a wire mesh type filter (mesh #3600, nominal opening 5 μm) as a filtration test filter, ethylene glycol slurry was suction-filtered under the following conditions, and the filtration rate (a certain amount The filterability of the slurry was evaluated based on the time required to filter the slurry (time required to filter the slurry) or the degree of clogging of the filter.

Condition (4) Maximum protrusion height A section of the reference length (2.5 m) was extracted from the cross-sectional curve obtained by a surface roughness measuring instrument (SE-3F) made by Koita Research Institute (hereinafter referred to as the extracted section). ) was sandwiched between two straight lines parallel to its center line, the distance between these two straight lines was measured, and the value expressed in micrometers (μm) was taken as the maximum height of the extracted portion. The maximum height was determined by determining 10 cross-sectional curves of the sample film cross-section, and was expressed as the average value of the maximum height of the wiped portion determined from these cross-sectional curves. The radius of the stylus used was 2.0 μm, and the load was 30
The cut-off value for (2) is 0.08.

(5) Number of coarse protrusions Aluminum was deposited on the film surface and measured using a three-beam interference microscope. The measurement wavelength was 0.54 μm, and the number of interference fringes showing third-order or higher order was calculated per 10 cia.

(6) Hard chrome-plated metal roll with fixed running properties (diameter 611Il)
) When wrapping the film, contact it at an angle (θ) of 135”.
A load of 53 g (Tz) was applied to one end, and it was run at a speed of 1 m/min to measure the resistance force (Tl+g) at the other end, and the coefficient of friction (μd) during running was determined using the following formula.

l　　　　T　IT　.

μd= in =0.4244! nθ
T2 53 Example 1 [Manufacture of crosslinked polymer particles] 5.0 parts of potassium persulfate as a water-soluble polymerization initiator and 0 parts of sodium lauryl sulfate as a dispersion stabilizer in 1000 parts of demineralized water.
．． After adding 0.004 parts of styrene and dissolving it uniformly, add 80 parts of styrene.
A mixed solution of 20 parts of divinylbenzene and 20 parts of divinylbenzene was added. Next, a polymerization reaction was carried out at 70° C. for 8 hours while stirring under a nitrogen gas atmosphere. The reaction rate was 98%, and the average particle size of the obtained particles was 0.60 um, dzs/d, and s value was 1.32. Further, the particle concentration of the obtained water slurry was 9% by weight.

[Drying of crosslinked polymer particles]

The resulting water slurry of crosslinked polymer particles was dried using a spray dryer (model: Mobil Minor, manufactured by Ashizawa Niro Atomizer ■) under the following conditions.

Conditions: The outlet temperature of the dried particles was 55°C, and the moisture content of the obtained particles was 8.4% by weight.

[Dispersion of crosslinked polymer particles in ethylene glycol] 10 parts of the obtained dry particles were added to 90 parts of ethylene glycol, and using a homomixer (Model: T, Ni, Homomixer SO type manufactured by Tokushu Kika Kogyo), After stirring at 1000 rpm for 30 minutes, use an ultrasonic dispersion machine (model US manufactured by Nippon Seiki).
300 to 20 kHz) for 60 minutes. The resulting slurry had good dispersibility.

[Production of polyester]

100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.09 parts of magnesium acetate tetrahydrate were placed in a reactor, heated to raise the temperature, and methanol was distilled off to perform a transesterification reaction, which took 4 hours from the start of the reaction. The temperature was raised to 230'C to substantially complete the transesterification reaction. Then, after adding 6 parts of the above slurry,
0.04 part of ethyl acid phosphate was added, and further 0.04 part of antimony trioxide was added to carry out a polycondensation reaction for 5 hours to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65. After drying the obtained polyester, 290°
After melt extrusion at C to form an amorphous sheet, 11
The film was stretched 3.5 times at 0°C, 3.7 times in the transverse direction at 120°C, and heat treated at 210°C for 3 seconds to obtain a film with a thickness of 15μ.

Example 2 Dried particles were obtained in the same manner as in Example 1, except that the water slurry supply rate of the crosslinked polymer particles was changed to 3.6 f/hr under the drying conditions of the spray dryer. A film was manufactured according to method 1 and its properties were measured.

Example 3 In Example 1, during the drying conditions after spray drying, the inlet temperature was 300°C, the amount of water slurry supplied for crosslinked polymer particles was 5.21. Dry particles were obtained in the same manner as in Example 1, except that the dry particles were changed to /hr, and a film was produced according to the method of Example 1, and its properties were measured.

Example 4 In Example 1, the composition of the crosslinked polymer particles during production was 20 parts of methyl methacrylate, 60 parts of ethylene glycol dimethacrylate, 20 parts of divinylbenzene,
Example 1 except that the polymerization initiator was changed to 1 part of potassium persulfate.
Crosslinked polymer particles were produced in the same manner as above. The reaction rate is 98
The average particle size of the particles obtained in % is 0.35 p m,
The d zs/d ts value was 1°27 and the particle concentration of the water slurry was 9% by weight. The obtained particles were dried in the same manner as in Example 1, a film was produced according to the method of Example 1, and its properties were measured.

Example 5 In Example 4, dry particles were obtained in the same manner as in Example 1, except that the water slurry supply rate of the crosslinked polymer particles was changed to 5.2 f/hr under the drying conditions of the spray dryer. A film was manufactured according to method 1 and its properties were measured.

Comparative Example 1 In Example 1, instead of drying using a spray dryer, 90 parts of ethylene glycol was added to 110 parts of a water slurry of crosslinked polymer particles, and water was removed using an evaporator under heating and reduced pressure. Using the obtained slurry, a film was obtained in the same manner as in Example 1, and its properties were measured.

Comparative Example 2 The procedure was the same as in Example 1 except that the drying conditions of the spray dryer were changed to 300°C inlet temperature and 2.81/hr water slurry supply rate for crosslinked polymer particles. The dry particles were obtained and a film was prepared according to the method of Example 1 and its properties were measured.

Comparative Example 3 In Example 1, the drying conditions of the spray dryer were changed to 200' inlet temperature and the water slurry supply rate of C1 crosslinked polymer particles was changed to 5.21/hr. The dry particles were obtained and a film was prepared according to the method of Example 1 and its properties were measured.

Comparative Example 4 In Example 1, the monomer composition during the production of crosslinked polymer particles was 240 parts of styrene, 60 parts of divinylbenzene, 12 parts of potassium persulfate as a polymerization initiator, and 0.012 parts of sodium lauryl sulfate. Crosslinked polymer particles were produced in the same manner as in Example 1 except for the following changes. The reaction rate was 97%, and the average particle size of the particles obtained was 0.70 μm, d zs/
The dts value was 1.36 and the particle concentration of the resulting water slurry was 23% by weight. Using the obtained water slurry, the particles were dried in the same manner as in Example 1, and a film containing such particles was obtained according to the method of Example 1, and its properties were measured.

The results obtained above are summarized in Table 1 below.

[Effects of the Invention] The crosslinked polymer particles obtained by the method of the present invention have excellent dispersibility, are useful as additives to polyester, and have high industrial value.

Claims (1)

[Claims] (1) When drying a water slurry containing 0.5 to 20% by weight of crosslinked polymer particles with a primary particle size of 0.05 to 3 μm using a spray dryer, the water content of the particles after drying is 2 to 15%.
% by weight.