JPH02104725A - Production of inorganic fiber - Google Patents

Abstract

PURPOSE:To obtain an inorganic fiber having high strength and elastic modulus and good wettability to metals and plastics by reacting a polysilastyrene with a metal alkoxide under specific condition, spinning the resultant polymetallocarbosilastyrene and subjecting the spun fiber to infusibilization and calcination. CONSTITUTION:A polymetallocarbosilastyrene having a number-average molecular weight of 500-1,000,000 is produced by reacting (A) a polysilastyrene having a main chain skeleton of formula I (x is 0.1-3; n is >=10) and having a number- average molecular weight of 200-500,000 with (B) a metal alkoxide of formula II (M is Ti or Zr; R is 1-20C alkyl or phenyl) at as ratio (III/IV) of (2-200)/1 under heating in an inert atmosphere. A spinning dope containing the product is spun and the obtained fiber is infusibilized and then calcined in vacuum, in an inert gas or in a reducing gas atmosphere at 800-1800 deg.C to obtain the objective fiber.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a method for producing inorganic fibers that have high strength and elastic modulus, and have good thermal properties with metals or plastics that constitute the matrix of composite materials. Regarding.

(Prior art) JP-A-62-256710 describes a new method for producing silicon carbide fibers in which polysilastyrene is heat treated to prepare a polycarbosilastyrene copolymer, and this copolymer is spun. , a method for producing silicon carbide fibers has been proposed in which spun fibers are made infusible and then fired.

The above publication states that the proposed method has a simpler manufacturing process than the known method for manufacturing silicon carbide fibers from polycarbosilane obtained by heating rearrangement reaction of polydimethylsilane.

However, the silicon carbide fibers obtained by the above method, like the silicon carbide fibers made from polydimethylsilane, have the essential problem that they do not have sufficient thermal resistance with the metals or plastics that make up the matrix of composite materials. It has points.

Japanese Patent Publication No. 58-5286 discloses a method of producing inorganic fibers by spinning polytitanocarbosilane obtained by reacting polycarbosilane and titanium alkoxide, making the spun fibers infusible, and then firing the infusible fibers. The manufacturing method is disclosed.

According to this method, it is possible to obtain an inorganic fiber that has good thermal properties with the metal or plastic that constitutes the matrix of the composite material. By the way, the spun polymer and spun fibers used in this method are sensitive to oxygen or moisture in the air, and in order to obtain inorganic fibers of stable quality, the spun polymers and spun fibers must be treated strictly until the infusibility treatment of the spun fibers is completed. Each process must be performed in a controlled atmosphere. For example, the above-mentioned spun fibers are gradually oxidized even in air at room temperature, and a glassy layer is formed on the fiber surface due to oxidation, and during the infusibility treatment, oxygen diffusion into the inside of the spun fibers is inhibited, resulting in a uniform composition. Infusible fibers may not be obtained, and as a result, variations may occur in the physical properties of the finally obtained inorganic fibers.

(Technical means for solving the problems) The present invention solves the problems in the known techniques as described above, and has extremely good thermal properties with the metal or plastic that constitutes the matrix of the composite material. Provided is a method for stably producing inorganic fibers with high strength and elastic modulus.

According to the present invention, the number average molecular weight having a main chain skeleton represented by the general formula (wherein, X is a number satisfying 0.1≦X≦3, and n is 10 or more) is 200. ~500,000 polysilastyrenes and general formula M(OR)4(n)(
In the formula, A represents Ti or Zr, and R represents an alkyl group having 1 to 20 carbon atoms or a phenyl group. ) is the CH of polysilastyrene.

Total number of structural units of -A-S i +- versus metal alkoxy CH.

The ratio of the total number of structural units of →MO← is 2 = 1 to 200
: By heating and reacting in an atmosphere inert to the reaction at a quantitative ratio within the range of 1, at least a part of the silicon atoms of polysilastyrene are bonded to h of the metal alkoxide via oxygen atoms. , a first step of producing polymetallocarbosilastyrene having a number average molecular weight of 500 to 1,000,000; a second step of preparing a spinning stock solution of polymetallocarbosilastyrene and spinning it; spinning the spun fibers under tension or without tension; No. 31 that becomes infusible under tension
step; and a fourth step of firing the infusible spun fibers at a temperature in the range of 800 to 1,800° C. in vacuum in an inert gas or reducing gas atmosphere.

Each step of the present invention will be explained below.

In the first step, from polysilastyrene represented by formula (I) and metal alkoxide represented by formula (II),
Prepare polymetallocarbosilastyrene.

Polysilastyrene can be prepared by methods known per se, e.g. U.S. Pat.
According to the method described in Publication No. 071, dichlorodimethylsilane and hydichlorostyrene are reacted in an inert organic solvent such as toluene or xylene in the presence of a sodium metal catalyst at a temperature below the melting point of the above raw materials for 8 cycles. can be manufactured.

The preferred value of X in formula (1) is 0.3 to 0.9, and the preferred value of n is 15 to 4,000.

Polysilastyrene and metal alkoxide are CI of polysilastyrene.

-(Total number of structural units of S i ← vs. metal alkoxy CI.

The ratio of the total number of structural units of DO→MO← is 2:1 to 200
: used for the reaction in a quantitative ratio within the range of 1.

The reaction temperature is 140~500'' C1, preferably 200~4
00°C.

The reaction between polysilastyrene and metal alkoxide is carried out in an inert atmosphere, such as a nitrogen or argon stream.

In this reaction, 5i-Si in polysilastyrene
Due to the radical rearrangement reaction and radical recombination generated by the dissociation of the bond, the cross-linking reaction between the Si-■ bond in the above formula and M (OR) a partially proceeds sequentially and concurrently, resulting in polysilane Polymetallocarbosilastyrene is formed in which at least some of the silicon atoms of styrene and a metal alkoxide base are bonded via oxygen atoms.

It has been confirmed from infrared absorption spectrum analysis and nuclear magnetic resonance spectrum that this polymetallocarbosilastyrene is mainly composed of the following structural units.

HL;611s　　　　1h CI, C) I.

-5i-CH2--5i-CH,- Si　CHz　- Hz CH.

-St　CHz　- C.I.

C1l.

■ Si CL - ■ C.I.

The average molecular weight of the polymetallocarbosilastyrene composed of each of the above-mentioned structural units is preferably from 500 to 1,000,000, particularly from 1.500 to 30,000, from the viewpoint of spinning performance.

In the second step, the polymetallo obtained in the first step,
There are no particular restrictions on the method for spinning polymetallocarbosilastyrene (spinning of carbosilastyrene) (it can be carried out according to a method known per se).

One method is to prepare a spinning solution by heating and melting polymetallocarbosilastyrene, and if necessary, filter the spinning solution to remove substances that are harmful during spinning, such as microgels and impurities. This is a method of spinning using a synthetic fiber spinning device.

The temperature of the spinning dope during spinning varies depending on the softening temperature of the raw material polymetallocarbosilastyrene, but is between 50 and 40°C.
Temperatures in the range 0'C are advantageous.

In the above-mentioned spinning device, after installing the spinning tube as necessary and setting the atmosphere of the spinning tube to an atmosphere selected from air, inert gas, hot air, hot inert gas, steam, or ammonia gas, the winding speed is adjusted. By increasing the size, fibers with a small diameter can be obtained. The spinning speed in melt spinning varies depending on the average molecular weight, molecular weight distribution, and molecular structure of the raw material polymetallocarbosilastyrene, but good results can be obtained in the range of 50 to 5,000 m/min.

Another spinning method is to prepare a spinning stock solution by dissolving polymetallocarbosilastyrene in its solvent, such as benzene, toluene, xylene, etc., and optionally remove substances harmful to the spinning by filtration as in melt spinning. remove, −
This is a method of dry spinning using a synthetic fiber spinning device on a boat.

In dry spinning, if necessary, a spinning tube is attached to the spinning device, and the inside of the tube is made into a mixed atmosphere of a saturated vapor atmosphere of the solvent and a gas selected from air and an inert gas, or gas, hot air, hot inert gas,
The solidification of the spun fibers in the spinning tube can be controlled by providing an atmosphere selected from steam, ammonia gas, hydrocarbon gas, and organosilicon compound gas.

Note that the spun fiber obtained in this step has excellent oxidation stability at room temperature compared to spun fiber of polymetallocarbosilane that does not have a phenyl group in the polymer molecular chain.

1. In the third step, the spun fibers are made infusible prior to firing in the fourth step.

One method of infusibility is to spin the spun fibers in an oxidizing atmosphere.
This is a method of holding at a temperature in the range of 50 to 400°C for several minutes to 30 hours under tension or non-tension. As a result, a molten oxide film is formed on the surface of the spun fiber,
The spun fibers are no longer eluted during firing, and fusion with adjacent fibers is prevented.

If the infusibility temperature is too low, an oxide film cannot be formed on the surface of the preventive fiber, and if the infusibility temperature is too high, oxidation may proceed too much.

The infusible atmosphere is preferably an atmosphere of one or more oxidizing gases selected from air, ozone, oxygen, chlorine gas, bromine gas, and ammonia gas.

Instead of making the spun fibers infusible in the oxidizing gas atmosphere described above, the spun fibers are immersed in an aqueous solution of an inorganic peroxide such as KMnOa, KzCrzOy, HlOt, etc.
A method of oxidation at a temperature in the range of 0°C can also be employed. In this case, the infusibility time is preferably 0.5 to 6 hours.

The molecular weight distribution of the polymetallocarbosilastyrene obtained in the first step of the present invention varies depending on the preparation conditions, and the softening temperature may be about 50° C. or lower depending on the content of low molecular weight compounds. In this case, it is preferable to reduce the amount of the low molecular weight compound in the addition step between the first step and the second step according to the method described later, so that the softening temperature of the polymetallocarbosilastyrene is 50° C. or higher.

Methods for removing low molecular weight compounds from polymetallocarbosilastyrene include extracting the low molecular weight compounds with methanol, alcohols such as ethanol, or ketones such as acetone, extracting polymetallocarbosilastyrene under reduced pressure or A method of removing low molecular weight compounds by distillation by heating at a temperature of 500° C. or lower in an inert gas atmosphere is exemplified.

Another method for making spun fibers infusible is to irradiate the spun fibers with ultraviolet rays, gamma rays, electron beams, etc., as necessary, in an oxidizing or non-oxidizing atmosphere, under tension or no tension, at room temperature. There is.

The irradiation dose is usually 10' to 1010 rads. By performing irradiation with ultraviolet rays, gamma rays, electron beams, etc. at a temperature in the range of 50 to 200°C, infusibility of the spun fibers can be completed in a shorter time.

If infusibility is carried out under no tension, the spun fibers may take on a wavy shape due to shrinkage, but this may be corrected in the fourth firing step, and tension is not necessarily required. When acting, the tension must be sufficient to prevent the spun fibers from shrinking and becoming wavy during infusibility, and is generally 1 to 500 g/+.

(2) In the fourth step, the infusible spun fibers are fired to prepare inorganic fibers.

Firing is carried out in vacuum, in an inert gas or reducing gas atmosphere, at a temperature in the range of 800 to 1,800°C, under tension or no tension.

During the firing process, the polymetallocarbosilastyrene constituting the infusible spun fiber releases easily volatile components through a thermal decomposition condensation reaction and a thermal decomposition reaction.

The release of this easily volatile component is greatest at 500 to 700°C, which causes the infusible spun fibers to shrink and bend, so applying tension during firing is advantageous in preventing this bending. .

The tension may be at least as large as possible to prevent the infusible spun fibers from becoming wavy even if they shrink during firing, and is practically 0.001 to 5k.
Preferably, the tension is in the range "g/mm".

Incidentally, the infusible spun fibers can be fired by a multistage firing method in which conditions such as atmosphere, temperature, and time are changed depending on the stage.

The inorganic fibers obtained in the present invention are: i) an amorphous substance consisting essentially of Sl5M, C and 0; ii) a solid solution consisting essentially of β-5fC, CSMC, β-5iC and 11c and/or MCl- , crystalline ultrafine particles with a particle size of 500 Å or less, and optionally an aggregate of the crystalline ultrafine particles and amorphous SiO□ and MO2,
and iii) a mixture of the amorphous substance of i) above and the crystalline ultrafine particles or aggregates of 11) above (in the above formula, h represents Ti or Zr, and X is a number greater than O and less than 1) ) consists mainly of inorganic substances selected from the group consisting of

The proportions of each element constituting the above-mentioned inorganic fibers, expressed in weight%, are generally Si2 30-60% M: 0.5-35%, preferably 1-10% C: 25
-40% 0: 0-20%.

(Effects of the Invention) The inorganic fiber obtained by the present invention has excellent mechanical strength, heat resistance, and oxidation resistance, and furthermore,
Compared to the silicon carbide fiber proposed in the publication, it has the advantage of having extremely good thermal properties with metals or plastics constituting the composite material, and low reactivity with metals.

Therefore, the inorganic fiber of the present invention can be applied to metals, plastics,
It can be suitably used as a reinforcing fiber material such as rubber, a fibrous heating element, a fireproof woven fabric, and an acid melt-resistant layer.

In addition, the spun fibers of the present invention are stable in air at room temperature, and no change in molecular weight or oxygen content is observed even if the fibers are left in the dark for several days. It is possible to stably produce inorganic fibers with excellent properties.

(Example) Examples are shown below.

Reference Example 1 Equimolar amounts of dichlorodimethylsilane and dichlorodimethylphenylsilane were polymerized at 110°C in the presence of a Na-dispersed catalyst in a toluene solvent to achieve a softening point of 86-9.
Polysilastyrene at 4°C was obtained. As a result of nuclear magnetic resonance analysis, this polysilastyrene was composed of polystyrene.

Example 1 Tetrabutoxytitanium Log was added to 40 g of polysilastyrene obtained in Reference Example 1, and after adding 10 ml of xylene, the temperature was gradually raised in a nitrogen stream, and when the temperature exceeded 100 ° C, stirring was stopped. It started. The temperature was raised to 350°C over 3 hours, maintained at this temperature for 2 hours, and then allowed to cool to room temperature.
43 g of polytitanocarbosilastyrene was obtained.

This polymer was confirmed by nuclear magnetic resonance analysis. Further, its number average molecular weight was 3.500.

The above polymer was charged into a spinning tube, and the tube was sufficiently purged with nitrogen.

The polymer was then heated to 300°C, maintained at the same temperature for 5 hours, cooled to 240°C, and spun at a winding speed of 500 m/min to obtain spun fibers with a diameter of 15 μm. This spun fiber was stable in air at room temperature, and no change in molecular weight distribution or oxygen content was observed even when it was left in the dark for 7 days.

The spun fibers were heated to 300°C in air for 30 hours to make them infusible, and then heat treated at 1,300°C in a nitrogen stream to obtain inorganic fibers.

This inorganic fiber has a weight ratio of St: 48χ, Tt: 5%
, C: 35χ and O: 12χ. In addition, the tensile strength of this inorganic fiber is 300 kg/mm.
The tensile modulus was 20t/aa''.

Bisphenol A type epoxy resin (X manufactured by Ciba Geigy)
After uniformly mixing 100 parts by weight of dicyandiamide curing agent (X82879B manufactured by Ciba Geigy) and 20 parts by weight of dicyandiamide curing agent (X82879B), the mixture was dissolved in a mixed solvent of methyl cellosolve and acetone at a weight ratio of 1:1. A 28-fold tχ solution was prepared.

After the inorganic fibers were impregnated with the solution, they were pulled in one direction using a drum wine gourd and heated for 10 minutes during open heat circulation.
By heating at 0"C for 14 minutes, a semi-cured inorganic fiber prepreg that was aligned in one direction was prepared. The fiber content of this prepreg was 60 volume χ and the thickness was 0.
．． It was 2 mm.

Layer 10 sheets of the above prepreg with the fiber direction aligned,
A unidirectionally reinforced epoxy resin composite material with a size of 250 m x 25 On+m was obtained by press molding at 30'C111 kg/ci for 90 minutes.

Width 12.7 mm, length 85 mm, thickness 2 from the above composite material
A sample for measuring the bending strength of the crow was cut out, and a three-point bending test with a span/width of 32 was conducted at a test speed of 2 torsos/min. The bending strengths of the composite material in the 0 degree and 90 degree directions were 178 kg/mm'' and 8,7 kg/w'', respectively.

Example 2 Example 1 was repeated except that 9.6 g of tetraisopropoxyzirconium was used instead of tetrabutoxytitanium. The obtained inorganic fiber has a weight ratio of Si; 45.
6χ, ZrB2.5χ, C, 33,5χ and O; 11.
It consisted of 4%. Further, the tensile strength of this inorganic fiber was 350 kg/mm'', and the tensile modulus was 21 t/mn''.

Claims (1)

[Claims] Represented by the general formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, x is a number satisfying 0.1≦x≦3, and n is 10 or more.) Polysilastyrene having a main chain skeleton and a number average molecular weight of 200 to 500,000 and the general formula M(OR)_4 (wherein, M represents Ti or Zr, and R has a carbon number of 1 to 20
represents an alkyl group or a phenyl group. ), the metal alkoxide represented by ▲mathematical formula, chemical formula,
There are tables, etc. The ratio of the total number of structural units of ▼ to the total number of structural units of metal alkoxide ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ is within the range of 2:1 to 200:1,
A heating reaction is carried out in an atmosphere inert to the reaction,
A first step of producing polymetallocarbosilastyrene having a number average molecular weight of 500 to 1,000,000 by bonding at least a portion of the silicon atoms of polysilastyrene with M of a metal alkoxide via an oxygen atom; 2nd step of preparing a spinning stock solution of polymetallocarbosilastyrene and spinning; 3rd step of infusible spun fiber under tension or no tension; infusible spun fiber in vacuum, inert gas or reducing gas A fourth step of firing in a gas atmosphere at a temperature in the range of 800 to 1,800°C. A method for producing inorganic fibers.