JPH02229298A - Acrylic flame resistant fiber paper and molded article - Google Patents

Abstract

PURPOSE:To obtain the fiber paper and molded article using a specific sulfur- containing aromatic polymer as a binder, being a specific value or above in oxygen index, having excellent flame retartance, heat resistance and flexibility and having dimensional stability even at high temperature (>=300 deg.C). CONSTITUTION:The aimed fiber paper and molded article using a sulfur- containing aromatic polymer (preferably containing poly-P-phenylenesulfide as main constitutional unit) as a binder and having >=28 oxygen index.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to acrylic (hereinafter abbreviated as PAN)-based flame-resistant fiber paper and molded products that have excellent flame retardancy, heat resistance, and flexibility. It is.

[Prior art] PAN flame-resistant fiber paper and molded products (hereinafter simply referred to as paper to avoid confusion) have excellent heat resistance, flame retardancy, electrical insulation, and heat insulation properties, and can be used as electrical insulation materials and heat-resistant packing. It is a useful industrial material for gaskets, heat-resistant filter insulation, honeycombs, wallpaper, aviation parts, etc.

As PAN-based flame-resistant fibers, air flame-resistant fibers are known in Japanese Patent Publication Nos. 37-4405 and 44-21175, and sulfur-containing PAN fibers are known in JP-A-63-50528. This fiber has high flame retardancy with an oxygen index + (LOI) of 40 or more, and is also a highly flexible fiber with a high elongation of 5 to 20% among heat-resistant fibers. However, when using the PAN-based flame-resistant fiber as PAN-based flame-resistant fiber paper and molded products, such high LO
There was a problem with commercialization because there was no binder that could take advantage of I and flexibility.

The inventors have discovered that F'A. N-based flame-retardant fiber paper and molded products were proposed in Japanese Utility Model Application Publication No. 1983-7199. In this paper, various types of binders were introduced as existing binders.

However, among existing binders, for example, aramid fibrils are expensive, polyvinyl alcohol-based,
Organic binders such as PAN and wood pulp have low flame retardancy, while inorganic binders such as mountain bark and pennite have poor flexibility. The results were not sufficiently satisfactory for obtaining fiber paper and molded products.

[Problems to be Solved by the Invention] The present inventors have improved the flame retardancy, heat resistance,
As a result of extensive research into binders that can take advantage of flexibility, the present invention was achieved with the prospect of solving the above problems by using sulfur-containing aromatic fibers as a binder.

[Means to solve the problem] The present invention has the following configuration.

(1) An acrylic flame-resistant fiber paper and a molded article, characterized in that the binder is a sulfur-containing aromatic polymer having a chemical structure represented by the following general formula, and the oxygen index is 28 or more.

(C6 H5 SOX) n − x = 0 to 2 ■ The sulfur-containing aromatic polymer is a sulfur-containing aromatic fiber.
The acrylic flame-resistant fiber paper and molded product described in .

(3) The acrylic flame-resistant fiber paper and molded article according to 2, wherein the sulfur-containing aromatic fiber is oxidized and infusible.

The present invention will be further described in detail below.

The PAN-based flame-resistant fiber that is the material of the present invention includes an air-based flame-resistant fiber and a sulfur-containing PAN flame-resistant fiber. Air flame-retardant fibers are made by heating PAN fibers in the air at 200 to 400°C.
It is a fiber obtained by reacting with PAN
The chemical structure reacts with oxygen in the air and cyclizes, improving heat resistance and flame retardancy.

Sulfur-containing PAN flame-resistant fibers are fibers obtained by reacting PAN fibers in a sulfur element-containing gas atmosphere at 230 to 500°C. PAN reacts with the sulfur element in the sulfur element-containing gas, and the heat resistance and flame retardance are improved due to the sulfur element cyclized structure and sulfur crosslinked structure.

Both the air-based flame-resistant fiber and the sulfur-containing PAN flame-resistant fiber have an LOI of 40 or more, which is a higher level than that of other organic fibers such as poly-m-phenylene phthalamide, which has an LOI of 30.

In particular, sulfur-containing PAN flame-resistant fibers have superior heat resistance, fiber strength, and fiber toughness compared to air flame-resistant synthetic fibers.
Therefore, the PAN flame-resistant fiber of the present invention contains sulfur-containing PA.
N flame-resistant fibers are preferred.

In order to obtain paper with high heat resistance and flame retardancy, which is the objective of the present invention, it is better to have a higher degree of progress in flame resistance, and the specific gravity of the PAN flame-resistant chemical fiber is at least 1.3, and more than 1.4. is preferred.

Furthermore, in order to improve the flexibility of paper, it is necessary to increase the elongation of the PAN-based flame-resistant chemical fiber, which is at least 5%, more preferably 5 to 20%.

Sulfur-containing PAN flame-resistant fiber can be cut with various cutters from 0.5 to
It can be cut into short fibers of lOOmm, preferably 20mm. Furthermore, after cutting, it can be pulverized using various types of pulverizers, either dry or wet.

Next, a sulfur-containing aromatic (hereinafter referred to as SPAR) polymer will be explained.

The chemical structure of SPAR has the following chemical formula, and a typical example is polyphenylene sulfide, particularly preferably poly p-phenylene sulfide (hereinafter referred to as P
l) S) is the main structural unit.

(C6H, SOx)n- x=0-2 Specifically, they are PPS, poly p-phenylene sulfoxide, poly p-phenylene sulfone, and copolymers thereof, or modified products thereof.

In the present invention, since the SPAR fiber is used as a binder for the PAN flame-resistant fiber paper, the fineness is 2d or less,
More preferably 0. 3 or less, more preferably 0.
It is preferably 1 or less.

Further, it is more preferable to mix fibers of various finenesses.

The flame retardancy of SPAR is easily influenced by shape. For example, PPS, which is one of the SPARs, has high flame retardancy (LOI is about 44 to 53) when it is in the form of a resin, but according to the inventor's experiments, for example, a film with a thickness of about 15 μm has a LOI of about 44 to 53. is as low as 25. Also, in the case of fibers, the LOI
is a polymer whose flame retardance is easily affected by the fiber diameter and form (cloth, felt string, etc.) of 24 to 30, and was initially thought to be unsuitable as a binder for PAN flame-resistant fiber paper according to the technical idea of the present inventor. .

Such SPA. The production of R-thin staple fibers is known from JP-A-63-152499.

This fiber with a fineness of 0.3 to 2 d can be produced by the usual melt spinning method, and in order to make fiber with a fineness of 0.3 d or less, polymer array fibers, polymer blends, etc.
The fibers can be spun by melt spinning methods such as peelable fibers, melt blowing, flash spinning, and the like.

Furthermore, in the case of polymer array fibers and polymer blends, it is preferable to remove the sheath component of the polymer array after spinning.

Peelable fibers require a peeling treatment. Further, these fibers can be cut into short fibers of 0.5 to 100 mm, preferably 0.5 to 20 mm, using various cutters. These short fibers can also be further fibrillated using a refiner, water jet, or the like. In addition, after cutting, it can be pulverized using various types of pulverizers, either dry or wet.

The SPAR fibers obtained in this way are very thin and have a large surface area and poor flame retardancy, and the LOI of paper made from 100% SPAR fibers was 24 as shown in Comparative Example 1. (Value indicating flame retardancy: LOI=28-3
2) Next, means for solving the flame retardancy of the PAN-based flame-resistant fiber binder obtained as described above will be explained.

In the flame retardancy of ordinary paper, the LOI is X1 and the volume ratio is V
Highly flame-retardant polymer component of X, LOI is Y, and volume ratio is V
When the flame retardance of the new mixed paper made of a low flame retardant polymer of Y is denoted by Z, the additivity as shown in the following equation does not hold.

Z=YVY +XVI Formula (1) In the case of ordinary paper, the LOI of the new mixed paper decreases rapidly just by adding a small amount of low flame retardant fiber to the high flame retardant paper. For example, L
FIG. 1 shows the results of an experiment conducted in Comparative Example 2 on a mixed paper in which a PAN flame-resistant fiber with an OI of 54 and a fibrillar acrylic fiber with an LOI of 19 were used as a binder.

By adding a small amount of fibrillar acrylic fiber (binder), the LOI decreases rapidly, and when the amount of acrylic fiber is 7% or more, the LOI becomes 28 or less. In other words, there was a drawback that flammability increased and practicality was lost.

If the addition rate of fibrillar acrylic fibers is less than 7%, papermaking properties will be poor and practical paper will not be obtained.

That is, it has been found that it is not practical to use fibrillar acrylic fibers as a binder due to flame retardancy and papermaking properties. (If a sample for measuring LOI is to be experimentally prepared, it can be prepared even with a fibrillar acrylic fiber addition rate of 5%, and the LOI at 105% in the comparative example was measured with such a sample.) This tendency is similar for other low flame retardant polymer binders such as polyvinyl alcohol and wood pulp.

In order to obtain highly flame-retardant paper, it is necessary to find a binder that can achieve the additivity as shown in formula (1). We conducted extensive research on various binders such as (adhesives and powders).

As a result, it was surprisingly found that SPA. P using R fiber as a binder
It was found that AN-based flame-resistant fiber paper exhibits a flame retardancy of 28 even at a high SPAR binder addition rate of 30%, as shown in Figure 1, and a practical binder addition rate of 8 to 20%. %, it has been found that a PAN flame-retardant fiber paper having a very high flame retardance with an LOI of 41 to 31 can be obtained.

Figure 1 shows PAN flame-resistant fiber with LOI = 54 and single yarn weave of 2.8 d and PP with LOI = 24 and single yarn fineness of 0.07 d.
This figure shows the relationship between the LOI of PAN flame-resistant fiber paper and the PPS addition rate when S fiber (a type of SPAR fiber) is used as a binder.

In this way, it has become possible to obtain highly flame-retardant PAN-based flame-resistant fiber paper only by forming the PAN-based flame-resistant fiber with SPAR fiber.

In order to enable the high-performance flame retardancy of the present invention, the content of PAN flame-retardant short fibers and SPAR short fibers is such that the amount of SPAR short fibers is 30 wt% or less of the total, and even 25 wt%.
% or less.

In other words, the flame retardancy of this paper, which is characterized by a high level of flame retardancy, is at least 28, preferably 32 or higher in LOI.

By using SPAR fibers as a binder in PAN flame-retardant fiber paper, highly flame-retardant paper can be obtained because the SPARs become extremely fine and their surface area increases, resulting in a rapid decrease in flame retardancy. This is thought to be due to a synergistic effect with the self-extinguishing properties inherent in SPAR fibers, as the flame and heat are separated by being dispersed as a binder in the PAN flame-resistant chemical fiber.

Adding thin SPAR short fibers as a binder to the PAN flame-resistant short fibers has the effect of making paper making very easy. (Example 1) PAN flame-resistant short fiber and S
Paper is made from water in which PAR staple fibers are dispersed. When making paper, if only PAN flame-resistant short fibers are used, as can be seen from Comparative Example 3, there is no entanglement and it is difficult to make paper. .

To obtain good papermaking properties, SPA. Preferably, the content of R fibers is at least 7%.

In addition, since the dispersibility of paper is good, it has the effect of improving flame retardancy. Although very thin SPAR short fibers have strong static electricity in the air and are difficult to disperse due to the adhesion between single filaments, they have been found to have very good dispersibility in water, making it easy to produce homogeneous paper. . This property is important in making flame retardant paper. As mentioned above, SPAR fibers have poor flame retardancy, so if they are poorly dispersed and become uneven in the paper, and agglomerated areas are formed somewhere, the flame retardance of the paper as a whole will decrease and the paper intended for the purpose of the present invention will not be produced. Although it cannot be obtained, very thin SPAR fibers have the characteristic of dispersing well in water and are highly flame-retardant PA.
Since N can be uniformly dispersed in the flame-resistant fiber,
This has the effect of improving the flame retardancy of the paper as a whole.

After drying, the strength of the manufactured paper can be increased by taking advantage of the characteristic that the SPAR short fibers have a melting point and fixing the SPAR fibers by pressure (partial fusion) at a temperature around the melting point. Also, SP
AR fibers are chemically stable and can improve the chemical resistance of paper.

PAN using SPAR fiber as a binder as in the present invention
Despite having such a high level of flame retardancy, flame-retardant fiber paper does not have the same properties as other papers, such as heat resistance, flexibility, electrical insulation, heat insulation, and chemical stability. It has excellent properties such as strength and strength.

In addition, in the manufacturing process, thin S
By using PAR short fibers as a binder and 17, uniform paper can be made and the high performance paper of the present invention can be achieved. Note that the sulfur element in the SPAR fiber is easily oxidized, and when oxidized, it is transformed into polyphenylene sulfonation, polyphenylene sulfoxide, etc., so that the SPAR fiber becomes "infusible."

When producing the paper of the present invention, there are cases where paper is made using infusible SPAR fibers, where paper is made from SPAR fibers, and where both are used in combination.

Infusible SP A. R fibers have the disadvantage of lower flexibility than unfusible SPAR fibers. Also, after paper making,
As a binder, SPAR fibers are softened below their melting point and fixed, but infusible SPAR fibers cannot use this property, so infusible SPAR fibers are used as binders. When using R fiber as a binder, it is preferably 0.3d or less,
Furthermore, it is desirable to devise ways to include many fine fibers such as 0.1 d or less.

Furthermore, by imparting infusibility, it has dimensional stability even at temperatures below 300°C and also has good chemical stability, so it can be used for various purposes such as gaskets, packing, and filters.

Unfusible SPAR fibers are used as infusible SPAR fibers in paper making.
It is preferable for the present invention because it does not require special considerations such as fibers.

Paper obtained using unfusible SPAR fibers as a binder can be made infusible by oxidation. As an oxidizing agent, sodium hypochlorite, acetic acid peroxide,
It can be treated with aqueous solutions such as potassium permanganate and hydrogen peroxide.

Example 2 shows an example of such infusibility.

The present invention includes molded products in addition to paper. In the case of a molded product, the SPAR may be used in the form of a polymer.

In addition to paper, molded products that can be made using the same method as the idea of the present invention include, for example, nonwoven fabric, felt, and sheets.

Furthermore, the present invention provides moldings of electrically insulating paper, battery separators, filters, friction materials, gaskets, packings, building materials, architectural interior materials, aviation interior materials, etc. made from the paper of the present invention and other molded products. Contains things.

In the past, electrical insulating paper only needed to be electrically insulating and heat resistant, but recently fires in high-rise buildings and electrical fires have been occurring frequently, so flame retardancy has become important. It's here. Of course, particularly high flame retardance is a good thing in the case of a direct fire, such as an electrical fire, but in the case of a building, it is also said that the fire spreads through the combustion of polymer insulation in the electrical piping. . Preventing the spread of fire within the building and electricity;
Securing communication arteries in the event of a fire (extending the lifespan of disconnections by even one minute) is important.

Meanwhile, the building has become a high-tech building, with wires running criss-crossed.
Workability, ie, flexibility, of wiring is required.

The paper and molded product of the present invention can be expected to be used as an electrical insulating material that not only has electrical insulation properties, heat resistance, and flexibility, but also has excellent flame retardancy for building fires.

By taking advantage of the flame retardancy, heat resistance, flexibility, electrical insulation, chemical stability, and infusibility of the paper of the present invention, it can be used for construction materials, architectural interior materials, aviation interior materials, electrical insulation materials, filters, and batteries. It can be used for many purposes such as separators, friction materials, and gaskets.

Examples of the PAN flame-resistant fiber paper and molded product according to the present invention will be specifically described below based on Examples and Comparative Examples.

[Example] In the present invention, the limiting oxygen index (LOI) is a value measured by the following measuring method.

Limiting Oxygen Index (LOI) 2 This is a value measured according to the measurement method specified in JIS-K-7201, and more specifically, it is as follows.

The measurement sample is cut into a width of about 15 mm (length of about 1.00 mm), dried, and then stored in a desiccator. At the time of measurement, the sample is taken out from the desiccator and fixed to the sample fixture in the combustion tube of the LO₂ measuring device.

A mixed gas of oxygen and nitrogen is added in it at 11, 41. /min
After flowing for about 30 seconds at a flow rate of
The minimum amount of oxygen (A
) and the nitrogen amount (B) at that time. The ratio of the oxygen flow rate to the total flow rate of the mixed gas is the LOI, which is expressed by the following equation.

LO 1 =A/ (A+B)

Example 1 Fiber length 5mm fineness 2.8d sulfur-containing PA A. 5, 10, 20, 3 using SPAR (especially PPS) short fibers with a fiber length of 5 mm and a fineness of 0.07 d as a binder to N flame-resistant short fibers.
When papermaking was carried out by adding 0▼Ol%, the papermaking properties were good at 10% or more. After the paper is dried, it is pressed to 270
The paper was heated at 0.degree. C. and partially pressed to obtain the heat-resistant, flame-retardant paper of the present invention.

The paper has a basis weight of 62 to 67 g/m2 and a flame retardant LOI of
As shown in FIG. 1, they were 44.38, 31, and 28, respectively. The volume electrical conductivity of this paper was measured to be 3.5X1
It exhibited good electrical insulation properties of 0.013Ω/cm.

Further, when the binder addition rate was 5%, the papermaking properties were poor, the strength was low, and the paper was easily torn.

Example 2 The paper obtained in Example 1 was further treated with a sodium hypochlorite solution at 95°C for 6 Qhrs. As a result, there was no dimensional change even at 350°C or higher, and the paper became infusible and had improved stability. , there was almost no change in the flexibility of the paper. In addition, flame retardant L
OI was 35.

Comparative Example 1 SPAR (especially PPS) with fiber length 5 mm and fineness 0.07 d
Short fibers were made using only a binder. After drying, the produced paper was heated and pressed at 250° C. in a press to obtain PPSIOO% paper. The paper has a basis weight of 63g/m2 and a flame retardant LOI of 2.
It was very low at 4.

Comparative Example 2 Fiber length: 5 mrn Fineness: 2.8 d Sulfur-containing PAN flame-retardant short fibers and fibrillated acrylic fibers having a fiber length of 5 mm were used as a binder.5. 10. When paper-making was carried out by adding 20 or 30 vol%, good paper-making was possible with 10% or more.

After drying, the produced paper was heated and pressed at 150°C in a press to obtain PAN flame-resistant paper with an acrylic fiber binder.

When the flame retardancy of this paper was measured, the LOI was <30.25 and 22.21 as shown in FIG. 1 for each of the above addition rates of fibrillar acrylic fibers. Further, when the binder addition rate was 5%, the paper formability was poor, the strength was low, and the paper was easily torn.

Comparative Example 3 Fiber length: 5 mm, fineness: 2.8 d, sulfur-containing PA When 100% N flame-resistant short fibers were made into paper without a binder, it was not possible to make paper.

[Effect of the invention] PA according to the present invention. By mixing SPAR fibers with a binder, it was possible to obtain PAN flame-resistant fiber paper and molded products with a flame retardancy of 33 or higher, which is quasi-nonflammable. This is an effect that cannot be imagined from the low flame retardance of SPAR fiber alone, which has an LOI of 24 or less.

In addition, the binder is also flexible and has excellent flexibility in paper and molded products.

Furthermore, by imparting infusibility, it has dimensional stability even at temperatures above 300°C and has good chemical stability, making it extremely versatile.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between binder fiber addition rate (v01%) and flame retardance: ultimate oxygen index (LOI), in which the data of Example 1 and Comparative Example 2 are plotted. Binder additive addition (VO1%) Figure 1

Claims (3)

[Claims] (1) An acrylic flame-resistant fiber paper and a molded article, characterized in that the binder is a sulfur-containing aromatic polymer having a chemical structure represented by the following general formula, and the oxygen index is 28 or more. -(C_6H_5-SOx)_n- x=0~2 (2) The acrylic flame-resistant fiber paper and molded article according to claim 1, wherein the sulfur-containing aromatic polymer is a sulfur-containing aromatic fiber. (3) The acrylic flame-resistant fiber paper and molded article according to claim 2, wherein the sulfur-containing aromatic fiber is oxidized and infusible.