JPH025769B2 - - Google Patents

Description

[Detailed description of the invention]

"Field of Industrial Application" The present invention relates to a method for imparting flexibility to liquid crystalline polyester, and more specifically, to a method for plasticizing liquid crystalline polyester within a range that maintains a low coefficient of linear expansion, liquid crystallinity, and compatibility. , relates to a method for imparting flexibility to liquid crystalline polyester, and is specifically characterized by reacting phenylenebisoxazoline with liquid crystalline polyester. "Prior art" US Patent No. 3778410, US Patent No. 3804805, J.Polym.Sci.Polym.Chem.Ed.p2043
(1976), WJ Jackson et al. first reported liquid crystalline polyesters that form anisotropic melts.Since then, liquid crystalline polyesters have attracted attention and numerous studies have been conducted. The liquid crystalline polyester reported by WJ Jackson et al. was a copolymer of polyethylene terephthalate and p-hydroxybenzoic acid. p-Hydroxybenzoic acid is 24 to 65 mol% (however, terephthalic acid residues and ethylene glycol residues are each considered as one constituent unit, and the mol% is
), with the strongest anisotropy occurring around 48 mol%. Since this melt is oriented under shear, its viscosity under shear decreases. The molded product extruded from the nozzle is highly oriented even without stretching, and the flexural modulus is
It showed a high value of 14Gpa. This molded product has high strength,
In addition to being highly elastic, it had the advantage of having an extremely small coefficient of linear expansion of less than 10 ^-5 °C ^-1 . "Problems to be Solved by the Invention" The inventors of the present invention measured the coefficient of linear expansion of the above-mentioned molded product using a more accurate measurement method, and found that the coefficient of linear expansion actually has a negative value near room temperature. I understood what happened. Specifically, -2×10 ^-6 to -7×10 ^-6
(°C ^-1 ). Although more than 10 years have passed since WJJackson's report, no concrete application products have been industrialized. One of the reasons for this is that the molded product has poor flexibility, is brittle against bending, and is easily broken. In order to improve this, it has been proposed to add a plasticizer, but it has not been found to be sufficient for practical use. Naturally, copolymerization of soft components has been considered, but sufficient effects have not been obtained. Japanese Patent Application Laid-open No. 59525, and Japanese Patent Application Publication No. 55-
Publication No. 145733 discloses reacting phenylenebisoxazoline with polyester.
The former discloses that when polyester is melted, the terminal carboxylic acid is reacted with phenylenebisoxazoline in order to suppress decomposition and at the same time the molecular weight is increased. In addition, in the latter case, all terminal groups
It is disclosed that when a polyester containing 50 mol% or more of carboxyl groups is reacted with phenylenebisoxazoline, the effect of increasing the molecular weight is particularly large. However, these publications do not mention anything about the effects on liquid crystalline polyesters that form anisotropic melts that are significantly different from conventional polyesters in terms of physical properties. For example, it is possible to plasticize and impart flexibility to liquid crystalline polyester without losing compatibility or liquid crystallinity when added in a limited amount, and while maintaining the advantage of a low linear expansion coefficient. There is no mention of anything being lost. ``Means for Solving the Problems'' and ``Actions'' The present inventors have worked diligently to develop a method for imparting flexibility to liquid crystalline polyester without losing its advantages of liquid crystallinity and low linear expansion coefficient. As a result of pursuing
The present invention was achieved by discovering that by reacting liquid crystalline polyester with a specific amount of phenylenebisoxazoline, flexibility can be imparted to liquid crystalline polyester without losing its advantages. That is, the present invention provides residues 24 to 64 of ()P-hydroxybenzoic acid having an intrinsic viscosity of at least 0.2.
mol%, () residues of terephthalic acid 38-18 mol%
and () 38 to 18 mol% of ethylene glycol residues [However, the molar ratio of () to () is 1. ]
A liquid crystalline polyester capable of forming an anisotropic melt composed of
0.1 to 4% by weight of the following general formula (However, in the formula, R ₁ to _{R 8} each represent a hydrogen atom or an alkyl group.) The liquid crystalline polyester is reacted with phenylenebisoxazoline while the liquid crystalline polyester is melted. This is a method of giving. The liquid crystalline polyester used in the present invention includes 1,
Using a viscosity measurement solvent with a weight ratio of 1,2,2-tetrachloroethane/phenol of 50/50, the concentration
The intrinsic viscosity measured at 0.5 g/dl at 30°C must be at least 0.2, preferably at least 0.4. If it is less than 0.2, sufficient strength cannot be exhibited even after reaction with phenylenepisoxazoline. The proportion of P-hydroxybenzoic acid in the liquid crystalline polyester used in the present invention must be 24 to 64 mol%. Outside this range no anisotropic melt is formed. In the present invention, among liquid crystalline polyesters forming an anisotropic melt, liquid crystalline polyesters containing 24 to 38 mol % of P-hydroxybenzoic acid residues are particularly preferred because of their large internal plasticizing effect. The liquid crystalline polyester capable of forming an anisotropic melt used in the present invention may be obtained by melt polymerization using an acetylated monomer as in conventional polyester synthesis, or may be obtained by melt polymerizing the monomer acid chloride. It may be synthesized using
A method disclosed in Japanese Patent Publication No. 56-18016 in which polyethylene terephthalate and P-hydroxybenzoic acid are heated and melted, a copolymerized polyester fragment is produced by acidolysis reaction under a stream of dry nitrogen, and then the pressure is reduced to increase the viscosity. The synthesized product has a large amount of carboxylic acid at the terminal end that can react with phenylenebisoxazoline, so flexibility is imparted particularly effectively. The liquid crystalline polyester used in the present invention contains a small amount (specifically less than 1 mol %) of diethylene glycol, propylene glycol, pentanediol, propanediol, butanediol, hydroquinone, resorcinol, 4, 4′-sulfonyldiphenol, 4,
It may be a diol component such as 4'-oxydiphenol or 2,6-naphthalenediol, or a copolymer of these derivatives, or a small amount (specifically less than 1 mol%) of malonic acid. , dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, suberic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-naphthalic acid, 2,6-naphthalenedicarboxylic acid, or derivatives thereof. may be copolymerized. The phenylenebisoxazoline used in the present invention is represented by the above general formula. Here, R ₁ to _{R 8} are hydrogen atoms or alkyl groups,
It is preferable that all of R ₁ to R ₈ are hydrogen atoms because synthesis is easy. A specific example of such a compound is 2,2'-P-phenylenebis(2-
oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-P-phenylenebis(4-methyl-2-oxazoline), 2,2-
P-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4
-methyl-2-oxazoline), 2,2'-m-phenylenebis(4,4'-dimethyl-2-oxazoline), and the like. The amount of phenylene bisoxazoline used is 0.1 per liquid crystalline polyester.
It should be ~4% by weight, preferably 1-3% by weight. If it is less than 0.1% by weight, there will be no substantial flexibility imparting effect, and if it exceeds 4% by weight, the plasticizing effect will be too large and the ability to form an anisotropic melt will be lost. The phenylenebisoxazoline may be added to the molten liquid crystalline polyester, or may be mixed in advance with the solid liquid crystalline polyester, such as chips or powder, and then melted and reacted.
Phenylenebisoxazoline may be used in solid form, for example, powder, or may be melted and used in liquid form. The reaction may also be carried out in batches,
It may be carried out using a continuous method such as an extruder. Since phenylene bisoxazoline is sublimable,
Since it is preferred to react in a closed system and this reaction is accompanied by thickening, reacting in an extruder is a preferred method. This reaction is preferably carried out at 320°C or lower to avoid decomposition. The reason why phenylenebisoxazoline imparts flexibility to liquid crystalline polyester is not clear, but after the reaction, the oxazoline ring opens and the flexibility of the methylene group formed allows liquid crystal molecules to break their rigid parts. It is presumed that this is due to plasticization. The liquid crystalline polyester obtained by the method of the present invention has a low coefficient of linear expansion and is imparted with flexibility, so it can be used, for example, in molding resins, composite materials, fibers, films, adhesives, etc. It can be used in a wide range of applications, including paints. Next, the present invention will be explained in more detail with reference to Examples. "Examples 1 to 4, Comparative Examples 1 to 5" Polyethylene terephthalate (5.2 mol) and P-acetoxybenzoic acid (4.8 mol) at 275°C,
A liquid crystalline polyester having an intrinsic viscosity of 0.65 was obtained by melting under a stream of dry nitrogen, allowing the acidolysis reaction to proceed for 70 minutes, and then reducing the pressure of the system for 5 hours to increase the viscosity (Comparative Example 1). At 280°C, 0.05% by weight of 2,2'-m-phenylenebis(2-oxazoline) was added to the melting polyester of Comparative Example 1.
(For polyester. The same applies hereinafter. Comparative Example 2),
0.3% by weight (Example 1), 1.0% by weight (Example 2),
3.0% by weight (Example 3) or 6.0% by weight
(Comparative Example 3) were added and reacted for 10 minutes each.
Further, a liquid crystalline polyester having an intrinsic viscosity of 0.35 (Comparative Example 4) was obtained in the same manner as Comparative Example 1 except that the reduced pressure thickening time was changed to 3.5 hours. While the polyester of Comparative Example 4 was melted at 280°C, 3% by weight (Example 4) or 6% by weight (Comparative Example 5) of 2,2'-m-phenylenebis(2-oxazoline) was added and reacted for 10 minutes. Ta. These reactants were extruded from a nozzle with a diameter of 0.5 mm at a shear of 1200 sec ^-1 at a temperature of 250 to 280°C to obtain a thread. Table 1 shows the linear expansion coefficient, Young's modulus, elongation, and liquid crystallinity measured for the obtained yarn. From Table 1, it can be seen that in Comparative Example 2, the amount added was small and there was no substantial effect of addition. In Examples 1 to 3, the Young's modulus decreased and the elongation increased compared to Comparative Example 1, even though flexibility was imparted.
It maintains the characteristics of low linear expansion coefficient (less than 2×10 ^-5 °C ^-1 ) and liquid crystallinity. Furthermore, it can be seen that this reaction is accompanied by an increase in intrinsic viscosity. The polyester of Example 4 has the same intrinsic viscosity as the polyester of Comparative Example 1, has a low coefficient of linear expansion, and has flexibility while maintaining liquid crystallinity. This shows that flexibility is not imparted by increasing the degree of polymerization. Since the polyesters of Comparative Examples 3 and 5 used too much phenylenebisoxazoline, they lost liquid crystallinity and also lost the advantage of low coefficient of linear expansion.

[Table] * Judgment by polarizing microscope "Examples 5 and 3" 2.1% by weight of 2,2'-P-phenylenebis(2-oxazoline) was added to the polyester of Comparative Example 1 melted at 280°C, Reacted product (Example 5), 2.1% by weight of 2,2'-m-phenylenebis(4-methyl-2-oxazoline)
was added and reacted (Example 6). Example 1 to each of the obtained polyesters
Measurements similar to those in 4 were performed, and the results are shown in Table 2. Both the polyester of Example 5 using P-type phenylenebisoxazoline and the polyester of Example 6 using phenylenebisoxazoline having a methyl group on the oxazoline ring have a lower coefficient of linear expansion and liquid crystallinity than the polyester of Comparative Example 1. It can be seen that flexibility is added while retaining the advantage of flexibility. "Comparative Example 6, Example 7" 4 moles of polyethylene terephthalate and 6 moles of P-acetoxybenzoic acid were reacted in the same manner as in Comparative Example 1, and a liquid crystalline polyester ( Comparative Example 6) was obtained.
100 parts by weight of the polyester of Comparative Example 6 and 2,2'-
Using a blender, the mixture was reacted with 3 parts by weight of m-phenylenebis(2-oxazoline) at 280°C for 10 minutes to obtain a liquid crystalline polyester (Example 7). The same measurements as in Examples 1 to 4 were performed on these, and the results are shown in Table 3. Table 3 shows that according to the present invention, flexibility can be imparted even to liquid crystalline polyesters having a high proportion of P-hydroxybenzoic acid residues.

[Table] * Determined by polarizing microscope

[Table] ± "Effect" determined by polarizing microscope As explained above, according to the method of the present invention,
A liquid crystalline polyester having a low coefficient of linear expansion and flexibility can be obtained, and the obtained liquid crystalline polyester can be used for molding resins, composite materials, fibers,
It can be used in a wide range of applications such as films, adhesives, and paints.

Claims (1)

[Claims] 1. ()P- having an intrinsic viscosity of at least 0.2.
Residues of hydroxybenzoic acid 24-64 mol%, ()
38-18 mol% of terephthalic acid residues and 38-18 mol% of ethylene glycol residues [However, ()
The molar ratio of and () is 1. ] and 0.1 to 4% by weight of the liquid crystalline polyester, which can form an anisotropic melt.
The following general formula for (However, in the formula, R ₁ to _{R 8} each represent a hydrogen atom or an alkyl group.) The liquid crystalline polyester is reacted with phenylenebisoxazoline while the liquid crystalline polyester is melted. How to grant.