KR20160139541A - Aramid paper for honeycomb and manufacturing method thereof - Google Patents

Abstract

The present invention relates to aramid paper for a honeycomb, and a method for producing the same. More specifically, the aramid paper for a honeycomb is mixed with aramid plucks and aramid pulp having a predetermined fiber length and a predetermined development level of fibrils at a predetermined ratio. More specifically, the aramid paper for a honeycomb comprises 20 to 40 wt% of the aramid plucks and 60 to 80 wt% of the aramid pulp. The method according to the present invention enhances the structure of a honeycomb according to the improvement of mechanical properties of raw paper and the improvement of porosity, thereby making produced aramide paper have lightweight. Also, feasibility of transferring raw paper is improved, and uniformity is strongly improved. Also, a coagulation problem between plucks can be resolved.

Description

Aramid paper for honeycomb and manufacturing method thereof

The present invention relates to an aramid paper for honeycomb and a method for producing the same, and more particularly, to an aramid paper for honeycomb prepared by mixing a certain percentage of aramid pulp having a fiber length of not less than a certain length and a development rate of fibril of not less than a certain length, And a method for manufacturing the same.

Paper is made using flock, pulp, and inorganic particles in an aqueous solution of paper-based honeycomb, and a laminate is formed and expanded with the produced paper to form a honeycomb and then impregnated and hardened with resin . On the other hand, in general, honeycomb using aramid fibers is produced by using aramid paper containing a binder or a resin coating on para-aramid fibers, pulp and other fiber materials. Typical examples of binders used for producing such aramid paper include US6551456 Discloses that a polyester fiber is used as a binder of aramid pulp to produce a porous paper, and that such paper can improve impregnation of a thermosetting structural resin. Korean Patent Laid-Open Publication No. 2009-0091811 discloses a technique for producing aramid paper using a thermoplastic fiber having a melting temperature exceeding a curing temperature of a matrix resin and a glass transition temperature of 100 ^o C as a binder. On the other hand, as a representative example of a manufacturing technique of a honeycomb paper through resin coating, Korean Patent Publication No. 2010-0094543 discloses a honeycomb paper using meta-aramid fibrid with a coating agent such as phenol, polyimide or epoxy Is described.

However, the aramid paper for honeycomb according to this conventional manufacturing technique has a constitution for a binder composed of a thermoplastic fiber or a resin which is essentially lower in strength than aramid pulp or fibrid than aramid, so that the mechanical property of the paper is deteriorated or the porosity There is a difficulty in lighter weight according to the present invention, and there is no concrete technique for solving the conveyance failure of the raw paper, the unevenness of the strength, and the flocculation between the flocs.

US 6551456 B KR 2009-0091811A KR 2010-0094543A

It is an object of the present invention to provide a honeycomb improved in physical properties through improvement of physical properties of aramid paper and a method of manufacturing the honeycomb.

One aspect of the present invention is to provide an aramid paper for honeycomb in which aramid flakes and aramid pulp are mixed at a certain ratio.

Another aspect of the present invention is to provide a method for producing an aramid paper for honeycomb which comprises blending a certain percentage of aramid pulp with a fiber length of at least a predetermined length and a fibril development rate of which is at least a certain level.

Another aspect of the present invention is to provide an aramid paper for honeycomb which solves the problem of conveyance failure of paper, uneven strength and cohesion between flocs, and a method for producing the same.

Since the physical properties of honeycomb are due to the physical properties of the raw paper, the strength of the honeycomb must be strong. However, since the honeycomb raw paper using the conventional aramid short fibers has a constitution for a binder made of thermoplastic fibers or resin which is essentially lower in strength than aramid pulp, flake, or fibrid than aramid, the mechanical properties of the paper are deteriorated or the porosity There is a disadvantage in weight reduction due to the decrease in the weight of the paper, and it does not provide a concrete technique for eliminating unevenness of strength and unevenness of cohesion between flocs.

Accordingly, in order to improve the physical properties of honeycomb, aramid paper, in which strength of paper is improved without using an additional binder by using para-aramid pulp, especially pulp having a long fiber length and fibril developed with aramid flock, / RTI >

The aramid paper for honeycomb according to the present invention may comprise a mixture of aramid flock and aramid pulp.

Further, the mixture may contain 20 to 40% by weight of the aramid flock and 60 to 80% by weight of the aramid pulp.

In addition, the length of the aramid flake is 4 mm to 8 mm, the length of the aramid pulp is 0.5 mm to 0.8 mm, and the aramid pulp has a fineness of 150 to 250 ml.

A method for producing an aramid paper for honeycomb according to the present invention comprises: preparing an aramid flock; Preparing an aramid pulp; Mixing the aramid flour and the aramid pulp at a ratio of 20:80 to 40:60 to prepare a feedstock; And a raw paper forming step of forming the paper stock as raw paper.

In addition, the length of the aramid flake is 4 mm to 8 mm, the length of the aramid pulp is 0.5 mm to 0.8 mm, and the aramid pulp has a fineness of 150 to 250 ml.

According to the present invention, it is possible not only to improve the mechanical properties of the aramid paper raw material for honeycomb, but also to improve the structure by improving the porosity of the honeycomb structure, as well as to improve easiness of transferring paper, uniformity of strength and cohesion between flocs.

The present invention relates to an aramid paper having improved strength of a paper without using an additional binder by using para aramid pulp, especially a pulp having a long fiber length and developed with fibril, together with aramid flock, will be.

The terms or words used in the present specification and claims are defined as follows but should not be construed to be limited to ordinary or dictionary meanings and the inventor shall not be construed to limit the scope of the term It should be construed as meaning and concept consistent with the technical idea of the present invention based on the principle that the concept can be properly defined.

"Fiber" means a unit of relatively flexible material having a high length to width ratio across a cross-sectional area perpendicular to the 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. A fiber spun in a package on a bobbin is called a continuous fiber. Fibers can be cut into short lengths called staple fibers. The fibers can be cut to a shorter length called floc. The yarns, multifilament yarns or tows comprise a plurality of fibers. Yarn can be entangled / entangled or twisted.

"Staple fibers" means filaments of 15 cm or less, preferably 3 to 15 cm; And most preferably 3 to 8 cm in length. The staple fiber is straight (i.e., non-crimped) or crimped to have a serrated crimp along its length at any crimp (or repeat bend) frequency. The fibers may be in an uncoated or coated, or pretreated (e.g., pre-stretched or heat-treated) form.

"Aramid" means a wholly aromatic polyamide, and is defined as a linearly-synthesized polymer characterized in that at least 60 mole% of the bonds connecting benzene rings are amide groups. The aramid is classified into para-aramid, meta-aramid and copolymers thereof at the substitution position of the amide group in the benzene ring. The para-aramid may be exemplified by polyparaphenylene terephthalamide and its copolymer, poly (paraphenylene) -copoly (3,4 diphenyl ether) terephthalamide and the like, and the meta-aramid may be poly (metaphenylene isophthalate) Amides and copolymers thereof. In the present invention, para-aramid can be more preferably selected.

 The term "aramid pulp" refers to a fibrillated microfiber made of aramid. The aramid pulp can be formed into a sheet form in a paper machine after being dispersed in water in order to have superfine properties like ordinary wood pulp. In order to improve the mechanical properties, To induce the fibrillation of individual short fibers in a dispersed state.

More specifically, in the method for producing and fibrillating aramid pulp, first, the wound aramid filament is cut using a rotary cutter to produce aramid staple fibers having a predetermined length. Next, washing is carried out to remove foreign substances in the aramid staple fibers, that is, fine powders or emulsions, and it is preferable to carry out the washing at a temperature of room temperature or higher in order to easily remove the foreign materials.

Then, the washed aramid staple fiber is dispersed in water to carry out a dissociation process for producing a homogeneous slurry. It is preferable that the dissociation process is performed at a temperature of room temperature or higher to further remove the remaining tanning agent and improve the dispersibility of the aramid staple fibers. Through the dissociation process, each of the aramid staple fibers is separated into a plurality of monofilaments. The concentration of the aramid staple fibers in the slurry is preferably 1.0 to 2.0% by weight.

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

Optionally, if the fibrillation of the aramid staple fibers does not proceed smoothly, the dissociation process and the beating process may be repeated.

The slurry containing the fibrillated aramid staple fibers through the beating process is made into a sheet, followed by a squeezing process to remove moisture from the grass first, and the firstly moisture-removed grass is dried Whereby the water is removed in the second order. The dried grass is then crushed to produce the final aramid pulp.

Meanwhile, the beating process is one of the important processes for determining the freeness of the aramid pulp (Canadian Standard Freeness). This is because the degree of fibrillation of aramid pulp varies greatly depending on the degree of fibrillation of the aramid staple fibers through the beating process. That is, when the degree of fibrillation is good, the degree of freeness of the pulp becomes low, which means that the dispersibility of the aramid pulp is excellent. On the other hand, if the degree of fibrillation is poor, the degree of freeness of the pulp becomes high, which means that the dispersibility of the aramid pulp is poor. It is also important that the aramid pulp has uniform physical properties. If the fibrillation is uneven, the deviation of the degree of freeness becomes large. As the deviation of Yeosu becomes larger, the final product to which it is applied also increases the defective rate because the difference of physical properties between products increases.

"Floc" refers to fibers of shorter length than staple fibers. The flocs have a length of about 0.5 to about 15 mm and a diameter of 4 to 50 micrometers, preferably of 1 to 12 mm and a diameter of 8 to 40 micrometers. Flocs less than about 1 mm do not significantly affect the strength of the material to be used. Flocs or fibers of greater than about 15 mm are generally not functioning because the individual fibers can entangle and can not be properly and homogeneously dispersed throughout the material or slurry. Aramid flocs can be produced by cutting aramid fibers to short lengths without significant or optional fibrillization, such as those produced by the methods described in, for example, U.S. Patent Nos. 3,063,966, 3,133,138, 3,767,756, and 3,869,430 .

By "fibrids" is meant non-granular, fibrous, or film-like particles. They have a melting point or decomposition temperature of at least 320 in the wind. Fibrids are fibers rather than fibers in that they have a fiber-like region 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 prime number of less than 1 micrometer. Prior to drying, the fibrids may be used in a wet state and deposited as a physically twisted binder around other components of the article. The fibrids may be prepared by any method, including using a fibridation 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 from a few microns to a few microns of less than one micrometer and a length of about 10 to 100 micrometers. The fibrils typically extend from the main trunk of a larger fiber having a diameter of 4 to 50 micrometers. The fibrils act as hooks or fasteners to trap adjacent materials. Some fibers are fibrillated, while other fibers are not fibrillated or effectively fibrillated, in which case the fibers are not fibrillated. Poly (meta-phenylene terephthalamide) fibers are readily fibrillated to produce fibrils during polishing. The poly (meta-phenylene isophthalamide) fiber is not fibrillated.

"Aramid flock" is a staple fiber made by cutting a continuous filament with a short length of unfibrilized aramid. The length of the aramid flock is usually 1 to 50 mm, and if the length is less than 1 mm, And when the length is 50 mm or more, it is known that it is not preferable because the possibility of occurrence of tangling is large when the sheet is formed, which tends to cause bonding.

However, in the present invention, when the flock having a diameter of 3 mm or less is used, the transfer of the paper is difficult and the irregularity of the strength is caused. When the diameter is 9 mm or more, cohesion between the flocks occurs and the length of the aramid flock is 4 mm to 8 mm Is preferable for the production of aramid paper for honeycomb.

It is more preferable to use 60 to 80% by weight of aramid pulp and 20 to 40% by weight of aramid flake in the production of aramid paper for honeycomb.

Hereinafter, the aramid paper for honeycomb of the present invention and the method for producing the same will be described in detail with reference to examples.

Preparation Example 1: Preparation of an aramid flock

1000 kg of N-methyl-2-pyrrolidone was maintained at 80 ^° C, and 80 kg of calcium chloride and 48.67 kg of para-phelenediamine were dissolved to prepare an aromatic diamine solution. The aromatic diamine solution is introduced into a reactor for polymerization and a molar amount of terephthaloyl chloride such as para-phenylenediamine is introduced into a reactor for polymerization and then stirred to obtain a poly (para-phenylene terephthalate) having an intrinsic viscosity of 6.8 Amide) polymer.

The polymer thus prepared was then dissolved in 99% concentrated sulfuric acid to prepare an optically anisotropic radiation dopant having a polymer content of 18% by weight. The prepared spinning dope was spinned using a spinneret and then solidified in a coagulation bath through an air layer to produce a filament. The filament was washed with water and dried, and then wound by 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 length (3, 6, 9 mm) and used as an aramid flock.

Production Example 2: Preparation of aramid pulp

20 kg of the 6 mm long aramid flake prepared in Preparation Example 1 was dispersed in 1,000 L of water to prepare a homogeneous slurry. The slurry thus prepared was added to a refiner equipped with a refiner and then stirred for a predetermined time. After sampling, the specific surface area (SSA) of the aramid pulp, the Canadian Standard Freeness (CSF) and the fiber length Fiber Length: FL), which was used to control the basic properties of aramid pulp. The slurry after the beating process was dehydrated using a filter, dried and stored. The dried grass was crushed into small pieces using a pulverizer to prepare a final aramid pulp.

Example 1: Production of aramid paper for honeycomb

3 kg of the 6 mm long aramid flake prepared in Preparation Example 1 and 7 kg of the aramid pulp prepared in Preparation Example 2 were dispersed in 1,000 L of water to prepare a homogeneous slurry. The slurry thus obtained was made into a papermaking form, the water was removed from the squeezing roll, and the water-removed grass was dried at a temperature of 105 ^° C at a speed of 5 m / min using Yankee dry. After 250 ^o C by using a hot roller temperature to prepare a honeycomb komyong aramid paper having a basis weight of 50g / m ² to 3m / min speed.

Comparative Example 1

Aramid paper for honeycomb was prepared in the same manner except that the aramid flock of Example 1 and the 3 mm and 9 mm lengths were used.

Comparative Example 2

Aramid paper for honeycomb was prepared in the same manner as in Example 1 except that 5 kg of aramid flock and aramid pulp were used, respectively.

Property evaluation

1) Specific Surface Area (SSA) measurement

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

2) Fiber Length (FL) measurement

The weight average length was measured using a "FiberExpert" table top analyzer (also known as "PulpExpert FS" available from Metoso Automation, Helsinki, Finland). The analyzer took photographic images of the pulp with a digital CCD camera as the pulp slurry passed through the analyzer and the integrated computer then analyzed the fibers in the image and calculated the weighted average length thereof.

3) Degree of Fibrillization (DF) measurement

The degree of fibrillation (DF) was measured using a "FiberExpert" table top analyzer (also known as "PulpExpert FS" available from Metoso Automation, Helsinki, Finland) Respectively.

4) Measure Canadian Standard Freeness (CSF)

The Canadian Standard Freeness (CSF) is a well-known measure of water drainage from slurry or dispersion of particles. The degree of freeness was measured by TAPPI Test 227. The data obtained from the performance of the test is expressed in Canadian Standard Freeness, which represents the millimeter of water drained from the aqueous slurry under certain conditions. The higher the number, the higher the drainage of water and water. Small values indicate a tendency for the dispersion to drain slowly. The greater the number of fibrils, the lower the rate at which water is drained through the forming paper matte, so the freeness of the fleece is inversely proportional to the freeness of the pulp.

The physical properties of the aramid paper for honeycomb produced by the method of Example 1 and Comparative Examples 1 and 2 were measured and are shown in Table 1 below.

Basis weight
(g / m ² ) thickness
(mm) density
(g / cm ³⁾ strong
(N / mm ² ) MD CD Example 1 54 0.54 1.24 12.6 16.5 Comparative Example 1 51 0.61 1.14 5.4 10.4 Comparative Example 2 52 0.58 1.18 4.9 8.2

As shown in Table 1, aramid paper for honeycomb prepared by using 70 wt% of aramid pulp and 30 wt% of 6 mm long aramid pulp having a long fiber length and a large amount of fibril formation through the refining process was excellent in strength of the base paper .

On the other hand, in the present invention, when the flock having a diameter of 3 mm or less is used, the transfer of the paper is difficult and the irregularity of strength is generated. When the diameter is 9 mm or more, coagulation occurs between the flocks. Therefore, the length of the aramid flock is 4 mm to 8 mm Was preferable for the production of aramid paper for honeycomb.

In the production of the aramid paper for honeycomb, when the content of the aramid pulp is 50% or less, the strength is lowered. Therefore, the content of the aramid pulp is preferably 60 to 80% by weight, and the content of the aramid flock is 20 to 40% It is more preferable to use it.

Claims (9)

A aramid paper for honeycomb comprising a mixture of aramid flake and aramid pulp. The method according to claim 1,
Characterized in that the mixture comprises 20 to 40% by weight of aramid flock and 60 to 80% by weight of aramid pulp. The method according to claim 1,
Wherein the length of the aramid flake is from 4 mm to 8 mm. The method according to claim 1,
Wherein the length of the aramid pulp is 0.5 mm to 0.8 mm. The method according to claim 1,
Wherein the aramid pulp has a fineness of 150 to 250 ml. Preparing an aramid flock;
Preparing an aramid pulp;
Mixing the aramid flour and the aramid pulp at a ratio of 20:80 to 40:60 to prepare a feedstock;
And forming a base material from the ground material. The method for producing an aramid paper for honeycomb according to claim 1, The method of claim 6,
Wherein the length of the aramid flake is from 4 mm to 8 mm. The method of claim 6,
Wherein the length of the aramid pulp is 0.5 mm to 0.8 mm. The method of claim 6,
Wherein the aramid pulp has a fineness of 150 to 250 ml.