KR102201806B1 - Aromatic polyamide paper for electrical insulation and manufacturing method thereof - Google Patents

Abstract

The present invention relates to aramid paper for electrical insulating paper and a method for manufacturing the same, and more specifically, aramid pulp having a certain length of fiber length or less, development of fibrils is more than a certain amount, and content of fines is more than a certain ratio, together with aramid flocs. It relates to aramid paper for electrical insulating paper used by mixing ratio and a method of manufacturing the same. More specifically, it relates to aramid paper for electrical insulating paper containing 20 to 40% by weight of the aramid floc and 60 to 80% by weight of aramid pulp having a fine content of 20% by weight or more, and the aramid paper for electrical insulating paper according to the present invention The manufacturing method has excellent oil composition, and based on this, it is possible to not only reduce the weight by improving the uniformity of electrical insulation properties and mechanical properties and improve the structure of the base paper, but also improve the ease of transporting the base paper, improve the uniformity of strength, and solve the problem of cohesion between flocs. have.

Description

TECHNICAL FIELD [0001] Aromatic polyamide paper for electrical insulation and manufacturing method thereof

The present invention relates to a wholly aromatic aramid paper for electrical insulating paper and a method for manufacturing the same, and more specifically, aramid pulp in which the fiber length together with the aramid floc is less than a certain length, the development of fibrils is more than a certain amount, and the content of fines is more than a certain ratio The present invention relates to a wholly aromatic aramid paper for electrical insulating paper having a uniform electrical insulating property due to excellent paper synthesis produced by mixing a certain ratio and a method of manufacturing the same.

Typical uses of industrial paper include electrical insulating paper, honeycomb, separator, filter, and the like, and among them, electrical insulating paper, which is a sheet-like article having insulating properties, is widely used in various electrical products and parts. For example, in a mobile phone, it is known to be applied to the field of disposing insulating paper between them in order to electrically isolate a printed circuit board from a power supply device, or covering the surface of a high voltage cable with an insulating sheet.

In addition, electrical insulating paper used for mobile phones and high-voltage cables is required for additional predetermined heat resistance according to each application, so it has good electrical insulation and is an insulating sheet having heat resistance, which is made of aromatic polyamide (aramid), a kind of engineering plastic. In recent years, a lot of research and development has been conducted on the manufacture and application of a sheet composed of pulp or fiber.

However, since aramid pulp or fiber-only sheet generally lacks flexibility and strength, research and development to complement this strength and flexibility by mixing aramid fiber and other fibers as a binder have been conducted, and related to the prior art. The aramid insulating paper disclosed in Japanese Patent JP 2535418 B secures flexibility by lowering the bending stiffness by mixing aramid and polyester fibers, but has a disadvantage of lowering electrical insulation and heat resistance again. Japanese Patent JP 5591046 B uses polycarbonate fibers. It was mixed with aramid to slightly compensate for the disadvantages of heat resistance, but in terms of electrical insulation, it was not able to secure uniform electrical insulation compared to the insulating paper using only aramid.

Recently, in order to compensate for these shortcomings, Korean Patent Application Publication No. KR 2014-0040096 A uses 40 to 100% by weight of para-aramid film-type fibrid manufactured through a specific jet spin process other than aramid pulp, and inorganic fillers as a binder. A technology for manufacturing electrical insulating paper by mixing is disclosed, and in Korean Patent Application Publication No. KR 2014-0038935 A, a technology for manufacturing electrical insulating paper using aramid fibrid or pulp as an aramid microfilament and a non-resin type binder is disclosed. Are doing.

However, in addition to aramid pulp or fibrid, the electrical insulating paper according to the conventional manufacturing technology has a composition for a binder such as thermoplastic fiber or inorganic filler, which is essentially lower in strength than aramid. It has not been able to provide a specific technique for solving poor transfer of raw paper, uneven strength, and aggregation between flocs by improving the oil composition for uniform electrical insulation, which is an important property.

JP 2535418 B JP 5591046 B KR 2014-0040096 A KR 2014-0038935 A

The present invention has been derived to solve the above problems, and an object of the present invention is to provide a wholly aromatic aramid paper for electrical insulating paper having uniform electrical insulating properties through improvement of the paper composition of the aramid paper base paper, and a method for manufacturing the same. will be.

Another aspect of the present invention relates to a wholly aromatic aramid paper for electrical insulating paper and a method of manufacturing the same, in which a certain ratio of aramid pulp having a fiber length less than a certain length, fibril development is more than a certain amount, and fine powder content is more than a certain ratio To provide.

Another aspect of the present invention is to provide a wholly aromatic aramid paper for electrical insulating paper and a method for manufacturing the same, which solves the problems of poor transfer of the base paper, uneven strength, and cohesion between the flocs.

The properties of electrical insulating paper should be superior to the strength of the base paper for uniform electrical insulating properties. However, in addition to aramid pulp or fibrid, the conventional electrical insulating paper has a composition for binders such as thermoplastic fibers or inorganic fillers, which have a lower strength than aramid, and is particularly important in electrical insulating paper than improving the strength of the base paper. It has not been able to provide a specific technique for solving poor transfer of raw paper, uneven strength, and aggregation between flocs by improving the paper composition for uniform electrical insulation, which is a physical property.

Therefore, in the present invention, an additional binder is used by using a certain ratio of aramid pulp having a fiber length less than a certain length, fibril development is more than a certain amount, and fine content is more than a certain ratio together with para-aramid flocks for uniform electrical insulation of electrical insulating paper. There is provided a wholly aromatic aramid paper for electrical insulating paper with improved paper composition that can impart uniform electrical insulation of the base paper without the need, and a method for manufacturing the same.

The wholly aromatic aramid paper for electrical insulating paper according to the present invention may include a mixture of aramid flocks and aramid pulp having a fine content of 20% by weight or more.

The mixture may include 20 to 40% by weight of aramid flocks and 60 to 80% by weight of aramid pulp.

In addition, the length of the aramid flocks may be 4 mm to 8 mm, the length of the aramid pulp may be 0.5 mm to 0.8 mm, and the aramid pulp may have a freeness of 150 to 250 ml.

The method of manufacturing a wholly aromatic aramid paper for electrical insulating paper according to the present invention comprises: preparing an aramid floc; Preparing aramid pulp having a fine content of 20% by weight or more; A stock manufacturing step of preparing a stock by mixing the aramid floc and aramid pulp in a ratio of 20:80 to 40:60; It may include; a base paper forming step of forming the stock into a base paper.

In addition, the length of the aramid flocks may be 4 mm to 8 mm, the length of the aramid pulp may be 0.5 mm to 0.8 mm, and the aramid pulp may have a freeness of 150 to 250 ml.

The wholly aromatic aramid paper for electrical insulating paper according to the present invention has excellent paper composition, and based on this, the uniformity of electrical insulating properties and mechanical properties are improved, as well as lighter weight through improvement of the structure of the base paper, and the ease of transport of the base paper is improved, and the uniformity of strength is improved. And it is possible to solve the cohesion problem between the flocks.

In order to improve the uniformity of electrical insulating properties through improved oil synthesis of electrical insulating paper, the present invention provides a certain amount of aramid pulp with a fiber length less than a certain length, fibril development more than a certain amount, and a certain percentage of fines content together with para-aramid floc. The present invention relates to a wholly aromatic aramid paper for electrical insulating paper that provides uniform electrical insulation of the base paper without using an additional binder by using the ratio, and a method of manufacturing the same.

Terms and words used in the present specification and claims are defined as follows, but they should not be construed as being limited to the usual or dictionary meanings, and the inventors of the terms are used to describe their own invention in the best way. Based on the principle that the concept can be appropriately defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention.

"Fiber" means a unit of material that is relatively flexible with a high ratio of length to width across a cross-sectional area perpendicular to its length, and is used interchangeably with the term "filament". The cross-section of the filaments described herein can be of any shape, but is typically circular or bean-shaped. Fibers spun in a package on the bobbin are referred to as continuous fibers. Fibers can be cut into short lengths called staple fibers. Fibers can be cut into shorter lengths called flocs. Yarns, multifilament yarns or tows comprise a number of fibers. The yarn can be entangled and/or tangled.

"Staple fiber" refers to a filament of 15 cm or less, preferably 3 to 15 cm; And most preferably can be prepared by cutting to a length of 3 to 8 cm. Staple fibers are either straight (ie, non-crimped) or crimped to have a serrated crimp along their length at any crimp (or repeat bend) frequency. The fibers may be present in uncoated or coated, or pretreated (eg, pre-drawn or heat-treated) form.

"Aramid" means a wholly aromatic polyamide, and chemically structurally, it is defined as a linear synthetic polymer characterized in that at least 60 mol% of the bonds connecting the benzene ring are amide groups. Aramids are classified into para-aramids, meta-aramids, and copolymers thereof at the position of substitution of the amide group in the benzene ring. Examples of para-aramid include polyparaphenylene terephthalamide and copolymers thereof, and poly(paraphenylene)-copoly(3,4 diphenyl ether) terephthalamide, and meta-aramid is polymetaphenylene isophthalamide. An amide and a copolymer thereof are exemplified. In the present invention, para-aramid may be more preferably selected.

"Aramid pulp" is a fibrillated microfiber made of aramid. Aramid pulp can be dispersed in water and then formed into a sheet in a paper machine to have papermaking properties like ordinary wood pulp. In this case, a beating machine is used to improve mechanical properties. Induce fibrillation of individual short fibers in a dispersed state using equipment such as.

More specifically, in the method of manufacturing and fibrillating aramid pulp, first, aramid filaments wound up are cut using a rotary cutter to produce short aramid fibers having a predetermined length. Next, washing is performed with water to remove foreign substances, that is, fine powder or oil, etc. in the short aramid fibers. In order to easily remove the foreign substances, it is preferable to carry out at a temperature of room temperature or higher.

Then, the washed aramid short fibers are dispersed in water to perform a dissociation process to make a homogeneous slurry. The dissociation process is preferably performed at a temperature of room temperature or higher in order to additionally remove residual oil and improve the dispersibility of short aramid fibers. Each of the short aramid fibers is separated into a plurality of monofilaments through the dissociation process. The concentration of short aramid fibers in the slurry is preferably 1.0 to 2.0% by weight.

Subsequently, a beating process is performed on the slurry uniformly dispersed in water through the dissociation process. In the beating process, the short aramid fibers are separated and cut using a refiner, as well as fibrillated, to produce fibrillated short aramid fibers having an average length of 0.5 to 5 mm of the short aramid fibers.

Optionally, if fibrillation of the short aramid fibers does not proceed smoothly, the dissociation process and the beating process may be repeatedly performed.

The slurry containing short aramid fibers fibrillated through the beating process is made into a sheet, and then a squeezing process is performed to first remove moisture from the paper paper, and the paper from which moisture is first removed is dried. As a result, moisture is secondarily removed. Subsequently, the dried paper paper is crushed to prepare a final aramid pulp.

Meanwhile, the refining process is one of the important processes for determining the freeness of aramid pulp (Canadian Standard Freeness). This is because the degree of fibrillation of short aramid fibers through the beating process shows a large difference in the freeness of the aramid pulp. That is, when the degree of fibrillation is excellent, the freeness of the pulp decreases, which means that the aramid pulp has excellent dispersibility. On the other hand, if the degree of fibrillation is poor, the freeness of the pulp becomes high, which means that the dispersibility of the aramid pulp is poor. In addition, it is important that the aramid pulp has uniform physical properties. If the fibrillation is non-uniform, the variation in free water also increases. When the deviation of the freeness increases, the difference in physical properties for each product of the final product to which it is applied increases, and the defect rate increases.

“Flock” means fibers of shorter length than staple fibers. The flock has a length of about 0.5 to about 15 mm and a diameter of 4 to 50 microns, preferably a length of 1 to 12 mm and a diameter of 8 to 40 microns. Flocks that are less than about 1 mm do not significantly affect the strength of the material in which it will be used. Flocks or fibers larger than about 15 mm generally do not perform as well as individual fibers may become entangled and cannot be properly and homogeneously dispersed throughout the material or slurry. Aramid flocs are prepared by cutting aramid fibers into short lengths without significant or any fibrillation, for example as prepared by the methods described in U.S. Patent Nos. Is manufactured.

“Fibrid” means non-granular, fibrous or film-like particles. They preferably have a melting point or decomposition temperature of 320 or higher. Fibrids are not fibers but fibers in that they have fiber-like regions connected by a web. The fibrids have an aspect ratio of 5:1 to 10:1 and an average length of 0.2 to 1.0 mm. The thickness of the fibrid web is less than 1 or 2 micrometers and is typically a fraction of 1 micrometer or less. Prior to drying, the fibrids can be used wet and deposited as a physically twisted binder around other components of the product. Fibrids can be prepared by any method including using a fibriding apparatus of the type disclosed in U.S. Patent No. 3,018,091 in which the polymer solution is precipitated and sheared in a single step.

"Fibrils" means small fibers having a small diameter of a few to several micrometers of less than 1 micrometer and a length of about 10 to 100 micrometers. The fibrils generally extend from the main trunk of larger fibers with a diameter of 4 to 50 microns. Fibrils act as hooks or fasteners to snag and capture adjacent material. Some fibers are fibrillated, while others are not fibrillated or are not fibrillated effectively and in this case the fibers are not fibrillated. Poly(meta-phenylene terephthalamide) fibers are easily fibrillated when polished to produce fibrils. Poly(meta-phenylene isophthalamide) fibers are not fibrillated.

"Aramid Flock" is a short fiber manufactured by cutting continuous filaments into short, non-fibrillated lengths made of aramid. The length of the aramid floc is usually about 1 to 50 mm, and if the length is less than 1 mm, the reinforcing effect of the sheet is If the length is reduced and the length is 50 mm or more, it is known that it is not preferable because the possibility of occurrence of entanglement is high when forming the sheet, and it is easy to cause bonding.

However, in the present invention, when a floc of 3 mm or less is used, it is difficult to transfer the raw paper as well as uneven strength occurs, and when it is 9 mm or more, agglomeration between the flocks occurs, and the length of the aramid floc is 4 mm to 8 mm. The case is preferable for the production of aramid paper for electrical insulating paper.

In addition, in the production of aramid paper for electrical insulating paper, it is more preferable to mix and use 60 to 80% by weight of aramid pulp and 20 to 40% by weight of aramid floc.

Hereinafter, aramid paper for electrical insulating paper of the present invention and a method of manufacturing the same will be described in detail with reference to Examples.

Preparation Example 1: Preparation of aramid floc

1,000 kg of N-methyl-2-pyrrolidone was maintained at 80 ^o C, and 80 kg of calcium chloride and 48.67 kg of para-femylenediamine were dissolved therein to prepare an aromatic diamine solution. The aromatic diamine solution was introduced into the polymerization reactor, and at the same time, molten terephthaloyl chloride in the same molar amount as para-phenylenediamine was added into the polymerization reactor, and then stirred to obtain a poly(para-phenylene terephthalate) having an intrinsic viscosity of 6.8. Amide) polymer was prepared.

Next, the prepared polymer was dissolved in 99% concentrated sulfuric acid to prepare an optically anisotropic spinning dope having a polymer content of 18% by weight. The prepared spinning dope was spun using a spinneret and then solidified in a coagulation bath through an air layer to prepare a filament. The filament was washed with water and dried, and then wound with a winder to obtain a poly(para-phenylene terephthalamide) filament. The poly(para-phenylene terephthalamide) filament was cut using a rotary cutter and cut into a predetermined length (3, 6, 9 mm) to be used as an aramid floc.

Preparation Example 2: Preparation of aramid pulp

A homogeneous slurry was prepared by dispersing 20 kg of aramid flocks having a length of 6 mm or more prepared in Preparation Example 1 in 1,000 L of water. The slurry thus prepared was put into a refiner equipped with a refiner, and then beaten for a certain period of time, and then sampled.Specific Surface Area (SSA), Canadian Standard Freeness (CSF), and Fiber Length: FL), etc., to control the basic properties of the aramid pulp, judged whether the beating process continued or not and proceeded with the beating process. The slurry after the beating process was dehydrated using a filter, dried and stored. The dried paper paper was crushed into small pieces using a grinder to prepare a final aramid pulp.

Preparation Example 3: Preparation of aramid pulp having a fine powder content of 20% or more

Of the aramid flocks of different lengths prepared in Preparation Example 1, 20 kg of aramid flocks mixed in a ratio of 10 to 20% by weight and 80 to 90% by weight of a 3 mm long floc was 1,000 Disperse in L of water to prepare a homogeneous slurry. The slurry thus prepared was put into a refiner equipped with a refiner, and then beaten for a certain period of time, and then sampled.Specific Surface Area (SSA), Canadian Standard Freeness (CSF), and Fiber Length: FL), etc., to control the basic properties of the aramid pulp, judged whether the beating process continued or not and proceeded with the beating process. The slurry after the beating process was dehydrated using a filter, dried and stored. The dried paper paper was crushed into small pieces using a grinder to prepare a final aramid pulp. This aramid pulp had a fine content of 20% or more.

Example 1: Preparation of aramid paper for electrical insulating paper

3 kg of 6 mm long aramid flocks prepared in Preparation Example 1 and 7 kg of aramid pulp having a fine powder content of 20% or more prepared in Preparation Example 3 were dispersed in 1,000 L of water to prepare a homogeneous slurry. After the slurry thus prepared was made into a paper type, moisture was removed from the squeezing roll, and the moisture-removed paper was dried at a rate of 5 m/min using Yankee Dry at 105 ^° C. Thereafter, aramid paper for electrical insulating paper having a basis weight of 250 g/m ² was prepared at a speed of 3 m/min using a hot roller at a temperature of 250 ^o C.

Comparative Example 1

A homogeneous slurry by dispersing 3 kg of 6 mm long aramid flocks prepared in Preparation Example 1 and 7 kg of aramid pulp not subjected to the process of increasing the additional fine powder content prepared in Preparation Example 2 in 1,000 L of water Was prepared. After the slurry thus prepared was made into a paper type, moisture was removed from the squeezing roll, and the moisture-removed paper was dried at a rate of 5 m/min using Yankee Dry at 105 ^° C. Thereafter, aramid paper for electrical insulating paper having a basis weight of 250 g/m ² was prepared at a speed of 3 m/min using a hot roller at a temperature of 250 ^o C.

Comparative Example 2

Aramid paper for electrical insulating paper was prepared in the same manner as in Example 1, except that 3 mm and 9 mm long aramid flocs were used.

Comparative Example 3

Aramid paper for electrical insulating paper was prepared in the same manner as in Example 1, except that 5 kg of aramid floc and aramid pulp were each used.

Property evaluation

1) Measurement of specific surface area (SSA)

The specific surface area (/g) was measured using the nitrogen adsorption method according to the BET measurement method.

2) Fiber Length (FL) measurement

The weight average length was measured using a "FiberExpert" tabletop analyzer (also known as "PulpExpert FS" available from Metso Automation, Helsinki, Finland). The analyzer took a photographic image of the pulp with a digital CCD camera as the pulp slurry passed through the analyzer, and then an integrated computer analyzed the fibers in the image to calculate its weight average length.

3) Degree of Fibrilization (DF) measurement

Degree of Fibrilization (DF) using a "FiberExpert" tabletop analyzer (also known as "PulpExpert FS" available from Metso Automation, Helsinki, Finland). Measured.

4) Canadian Standard Freeness (CSF) measurement

The Canadian Standard Freeness (CSF) is a well-known measure of the drainage of water from a slurry or dispersion of particles. Freeness was measured by TAPPI test 227. The data obtained from performing the above tests are expressed in Canadian standard freeness, representing the millimeters of water drained from the aqueous slurry under specific conditions. If the number is large, it means that Yeosu Island and water drainage are high. Small numbers indicate a tendency for the dispersion to drain slowly. The higher the number of fibrils reduces the rate at which water drains through the forming paper mat, so the degree of fibrillation of the pulp is inversely proportional to the free water.

The physical properties of the aramid paper for electrical insulating paper prepared by the method of Example 1 and Comparative Examples 1 to 3 were measured, and are shown in Table 1 below.

Basis weight
(g/m ² ) thickness
(mm) density
(g/cm ³ ) strong
(N/mm ² ) Genetic strength
(kV/min) MD CD Example 1 253 0.238 1.15 15.6 16.5 6.4 Comparative Example 1 251 0.252 1.02 6.9 11.6 5.6 Comparative Example 2 248 0.258 0.98 4.2 10.4 5.3 Comparative Example 3 254 0.232 1.2 3.9 8.5 5.9

As shown in Table 1, through the refining process, the fiber length is less than a certain length, fibril formation is large, and a fine content of 70% by weight of aramid pulp of 20% or more and 30% by weight of aramid flocks of 6 mm length are used. Aramid paper for electrical insulating paper has excellent dielectric strength.

On the other hand, in the present invention, when a floc of 3 mm or less is used, it is difficult to transfer the raw paper as well as uneven strength occurs, and when it is 9 mm or more, agglomeration between the flocks occurs, so the length of the aramid floc is 4 mm to 8 mm. It was found that the case of is preferable for the production of aramid paper for electrical insulating paper.

In addition, in the manufacture of aramid paper for electrical insulating paper, when the content of aramid pulp is 50% or less, a decrease in strength occurs, so the content of aramid pulp is preferably 60 to 80% by weight, and the aramid floc is mixed at 20 to 40% by weight. It was found that it is more preferable to use it.

Claims (2)

20 to 40% by weight of para-aramid flocks of 4 mm to 8 mm in length; and
It consists of a mixture of 60 to 80% by weight of para aramid pulp,
The para-aramid pulp contains 20% by weight or more of fine powder prepared using a refiner equipped with a refiner using an aramid floc in which a 6 mm length or more floc is mixed in a ratio of 80 to 90% by weight, and has a freeness of 150 to All aromatic aramid paper for electrical insulating paper, characterized in that 250 ml. Preparing a para-aramid floc having a length of 4 mm to 8 mm;
Para aramid flocks having a length of 6 mm or more are mixed in a ratio of 80 to 90% by weight, containing 20% by weight or more of fine powder, prepared using a refiner equipped with a refiner, and having a freeness of 150 to 250 ml. Preparing aramid pulp;
A stock manufacturing step of preparing a stock by mixing 20 to 40% by weight of the para-aramid floc and 60 to 80% by weight of the para-aramid pulp; And
Method for producing a wholly aromatic aramid paper for electrical insulating paper, characterized in that consisting of a base paper forming step of forming the stock into a base paper.