JPS63264663A - Polyurethane article of good yellowing resistance and its production - Google Patents

Abstract

PURPOSE:To obtain the titled article excellent in yellowing resistance, by coagulating a polymer solution based on a polyurethane elastomer in a specified nonsolvent by a wet process, washing the polymer, controlling the pH of the polymer to a desired value on the acid side and drying this polymer. CONSTITUTION:A polymer solution formed by dissolving a polymer based on a polyurethane elastomer in a solvent such as dimethylformamide is immersed in a mixture of nonsolvent and solvent such as DMF for said polymer to solidify the polymer by a wet process, and the polymer is washed to remove the solvent. This polymer is treated with an inorganic acid, an organic acid or its aqueous solution (e.g., aqueous citric acid solution) to control the pH to an acidity (in terms of a pH) of 6.9-3.5, and this polymer is dried.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The object of the present invention is to provide a polyurethane product that has good yellowing resistance against yellowing during processing, storage, or use of secondary products. .

[Prior Art] Many inhibitors have been developed and used to prevent polyurethane products from yellowing or deteriorating due to the effects of exhaust gas, combustion gas, light, etc.

Furthermore, many proposals have been made to prevent yellowing and deterioration. For example, Japanese Patent Publication No. 61-30075 discloses that the yellowing resistance of polyurethane products can be improved by adding hydroxycarboxylic acid or dicarboxylic acid to polyurethane containing two-component titanium. Since this is a problem, the present applicant has already proposed in Japanese Patent Publication No. 50-27494 to add an aliphatic hydroxycarboxylic acid to a polyurethane solution to stabilize storage. In addition, for storage stabilization
In the publication, the ionic dissociation constant is 5x 10 ~ lX10-6
It has been proposed to add acidic compounds selected from organic acids, inorganic acids, etc. and epoxy compounds to polyurethane solutions.

[Problems to be Solved by the Invention] The yellowing and deterioration inhibitors that have been proposed so far are effective in preventing the deterioration and embrittlement of polyurethane products, but there are almost no agents that can be expected to prevent yellowing.

In particular, polyurethane products that are coagulated by treating a polyurethane solution, especially a dimethylformamide solution of polyurethane in a non-solvent, or products that are coagulated by containing an antioxidant and/or a light stabilizer are susceptible to yellowing. Therefore, when these additives are not added, yellowing is improved, but deterioration and embrittlement cannot be prevented.

As a result of investigating the causes of yellowing, we found that polyurethane becomes alkaline when antioxidants and light stabilizers are added, and that when polyurethane is dissolved in an amide solvent, the resulting product becomes alkaline. It has been found that the addition of compounds (e.g. stabilizers, polymerization catalysts, etc.) with They also found that polyurethane products easily yellow when left alkaline.

Therefore, we investigated ways to make polyurethane products acidic. That is, Japanese Patent Publication No. 4B-526, in which a polyurethane solution, especially a polyurethane solution dissolved in an amide solvent, is wet-coagulated by adding a strong substance, such as an aliphatic carboxylic acid.
It has been found that the methods disclosed in Japanese Patent Publication No. 49-26702 do not provide sufficient acidity.

The present invention is to improve the yellowing of polyurethane products.

[Means for Solving the Problems] The present invention provides a polyurethane product made of a polymer mainly composed of a polyurethane elastomer, in which the l)H of the polyurethane constituting the product is 6.9 to 3.5. It is a polyurethane product with good yellowing resistance, which is characterized by a good yellowing resistance.

Furthermore, the present invention includes a step of wet coagulating a polymer solution mainly composed of a polyurethane elastomer in a non-solvent containing a polymer solvent to solidify the polymer, and then (a) washing the polymer. A method for producing a polyurethane product with good yellowing resistance, characterized by combining the following steps: l) a treatment step for adjusting H to a range of 6.9 to 3.5, and (c) a drying step. In the manufacturing method of polyurethane products, the PH of the polymer is After adjusting to a range of 6.9 to 3.5, nonionic or acidic with pH 6.9 or less or I) 86.9
This is a method for producing a polyurethane product with good yellowing resistance, which is characterized in that the polyurethane product is dissolved or dispersed in a solvent or dispersant having an acidic composition as shown below.

That is, in the present invention, a polymer solution in which a polymer mainly composed of polyurethane elastomer is dissolved using dimethylformamide, diethylformamide, dimethyl sulfoxide, diethyl sulfoxide, etc. as a solvent is added to a non-containing solution in which the solvent for the polymer is present. Polyurethane products remain alkaline even after immersion in a solvent to solidify the polymer using a wet coagulation process and subsequent washing to remove the polymer solvent. Therefore, polyurethane products or polyurethane-based polymer products are treated with organic acids or inorganic acids or aqueous solutions of these acids to adjust the pH to an acidity in the range of 6.9 to 3.5. Examples of organic acids used for pH adjustment include acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, trimethylacetic acid, caproic acid, n-hebutanoic acid, caprylic acid, pelargonic acid, etc. Carboxylic acid having less than 10 carbon atoms. Glycolic acid, β-oxypropionic acid,
Hydroxycarboxylic acids such as oxybutyric acid, malic acid, citric acid, and tartaric acid. At least one organic acid selected from halogenated carboxylic acids such as fluoroacetic acid, chloroacetic acid, dichloroacetic acid, bromoacetic acid, and α-chloropropionic acid. Examples of inorganic acids include hydrochloric acid, phosphoric acid, partially esterified or salted compounds, phosphorous acid, partially esterified or salted compounds, etc., preferably an aqueous solution. Process. If the pH after acid treatment is less than 3.5, it is not preferable because it will lead to a decrease in the strength of the polyurethane. After acid treatment, the polymer is deliquified, and if a large amount of acid is present, it is washed with water to remove excess acid, and then dried. Moreover, if the pH is within a predetermined value, it is preferable that the salt remains.

In addition, when using a dry coagulation method in the manufacturing method of polyurethane products, examples of solvents or dispersants for polymers mainly composed of polyurethane elastomers include hydrocarbon compounds such as benzene, toluene, xylene, heptane, and ligroin; A solvent selected from ketone compounds such as acetone, methyl ethyl ketone and diethyl ketone, and ether compounds such as dioxane and tetrahydrofuran is used. Furthermore, it may be dissolved in dimethylformamide, and after neutralization, dispersed in a dispersant or diluted with another solvent.

In addition, the polyurethane elastomer of the present invention has a hard segment in its molecular chain that is bonded by a urethane bond (-NHCOO-) or a urethane bond and a urea bond (-NH CO bond), and an ester bond, an ether bond, or a carbonate bond. Alternatively, it is an elastomer composed of soft segments made of a polymer with an average molecular weight of 500 to 3,500 bonded by lactone bonds. Furthermore, the polyurethane elastomer may contain less than 50% by weight of other polymers, such as polyvinyl chloride, polycarbonate, polyacrylic acid ester, acrylonitrile butadiene copolymer, styrene butadiene copolymer, polyimprene, etc., as necessary. It is a polymer mainly composed of added polyurethane elastomer. Antioxidants, such as 4,4°-butylidene bis(3-methyl-6
-t-butylphenol), 1.3.5; -tris(4
-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, 2,6-di-t-butyl-P-
Cresol, 4,4°-thiobis(3-methyl-6-t
-butylphenol) 1,2-bis(2,6-1-butyl-P-cresol)ethane, other phenolic compounds, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5- di-t-butylanilino)-1.3
,5. - Hindered phenolic compounds such as triazine, etc. Light stabilizers, UV absorbers, such as bis(2,
2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis(2,2,6,6-tetramethyl-4-
piperidyl) -1,2,3,4-butanetetracarposilate, 2-ethoxy-5-t-butyl-2-ethyloxalic acid bisanilide, 2(2'-hydroxy-5'-methylphenol) )-benzotriazole, 2-(2°-hydroxy-3-t-butyl-5-methylphenol)-5-chloro-benzotriazole, 2
．． It is preferable to add a compound selected from 4-dihydroxybenzophenone, ethyl-2-cyano-3,3-diphenylacrylate, other benzotriazole compounds, hindered amine compounds, etc. to impart deterioration resistance. In addition, additives selected from fungicides, colorants, softeners, fillers, flame retardants, etc. may be added as necessary.

Furthermore, the method for measuring the pH value of the polyurethane product of the present invention is as follows:
After making the sample to be measured into as fine a shape as possible, the bath ratio was adjusted to 100 g of ion-exchanged water to 10 g of the sample.
After heating to °C and processing for 3 hours, cool to temperature and p
Measure the pH with an H meter.

Furthermore, the yellowing resistance evaluation method for polyurethane products of the present invention is as follows:
A polyurethane product or polyurethane to be used is formed into a film and used as a sample. First, a sample was fixed in an almost vertical position in a glass container with a lid that had sufficient internal volume and was equipped with a stirring device capable of internal stirring.
A certain amount (501) l)m of NOx gas generated based on the "Dyeing Fastness Experimental Method for Nitrogen Gas" was injected into a sealed glass container and left indoors for 5 days.
The degree of discoloration of the sample is evaluated by visual judgment using a contamination gray scale and by instrumental colorimetric analysis using reflectance at a specific wavelength. The degree of discoloration of the latter is based on JIS Z-872.
9. Color difference Δb of Δb value defined in ``Representation method of object color using rt a b color system and TUV color system''
Evaluate discoloration by value.

The polyurethane products of the present invention can be used to produce products with excellent yellowing resistance, particularly as leather-like sheets for white or light-colored products, waterproof fabrics, and the like.

[Example] Next, embodiments of the present invention will be specifically described with reference to Examples.

Note that parts and percentages in the examples are by weight unless otherwise specified.

Example 1 A hindered amine compound was added as a light stabilizer for polyurethane to a dimethylformamide (abbreviated as IF) solution of polyester polyurethane obtained by reacting polyethylene adipate diol, 4,4-diphenylmethane diisocyanate, and ethylene glycol. [Screw(
A polyurethane composition solution containing 0.15% of 2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1.0% of titanium fermentation, and 2% of a tunic agent was poured onto a polyethylene sheet. D) It was spread and coated, immersed in a 30% IF aqueous solution to solidify, and washed with water to obtain a porous polyurethane sheet (A). A part of this porous polyurethane sheet was dried to obtain a control polyurethane sheet (sample 1), and the other part was treated in an aqueous citric acid solution, washed with water, and dried to obtain various types of polyurethane sheets.
1 of porous polyurethane sheets (Samples 2 to 7) were obtained.

l) of the porous polyurethane sheet for each of these samples.
Results of measuring H and yellowing degree Δb However, yellowing degree Δb
The larger the value, the more yellowing the yellowing is.

In other words, it has been experimentally confirmed that when the value of yellowing degree Δb shown in Table 1 is 1.5 or more, the product is likely to cause yellowing complaints, but the product of the present invention has less yellowing resistance. It was a polyurethane sheet.

Comparative Example 1 A porous polyurethane sheet was produced in the same manner as in Example 1 by adding 1.5% citric acid to the solution of the polyurethane composition of Example 1. The I)H value of this porous polyurethane sheet was 7.9, and the yellowing resistance was poor with a yellowing index of 4.6.

Example 2 An o+rl solution of polyether/ester polyurethane obtained by reacting a polymer glycol of 60% polytetramethylene ether glycol and 40% polyethylene adipate glycol with 4,4'-diphenylmethane diisocyanate and isophorone diamine was added to the polyurethane. On the other hand, hindered phenol compounds [
1,3,5-tris(4-1-butyl-3-hydroxy-2,6-dimethylpencyl)isocyanuric acid 0
．． D) A polyurethane composition solution containing 15% of a hindered amine compound as a light stabilizer and 2% of a coagulation regulator was cast onto one surface of a nonwoven fabric sheet impregnated with polyurethane, and D) immersed in a 45% IF aqueous solution. porous polyurethane sheets with various pH values (Samples 8 to 14)
I got it. Table 2 shows the results of measuring the pH and yellowing degree Δb of the porous polyurethane sheet for each of these samples.

Table 2 This is a porous polyurethane sheet with excellent yellowing resistance and deterioration resistance, and the artificial leather made from this sheet is suitable for internal use.

Example 3 80% polyethylene adipate glycol with an average molecular weight of 11500 and 20% polyethylene ether glycol were mixed into 4
．． A prepolymer was prepared by reacting 4-diphenylmethane diisocyanate in a mixed solvent of 80% tetrahydrofuran/20% toluene, and the chain was extended using isophorone diamine as a chain extender to obtain a 25% polyurethane elastomer solution. The l)H of this solution is 7.9.

Next, 47 parts of a 0.3% citric acid aqueous solution was added to 100 parts of the polyurethane elastomer solution to prepare a dispersion [IF] having a polyurethane elastomer concentration of 17%.

On the other hand, a polyurethane elastomer dispersion [n] was prepared by adding 0.2% of a hindered phenol liquefaction inhibitor and 0.10% of a benzotriazole light stabilizer to the polyurethane elastomer dispersion i[IF.

The dispersion liquid [IF and dispersion liquid [II] were applied to a polypropylene sheet in a liquid volume of 4709/7d, treated in warm air at a temperature of 50°C for 5 minutes, and then dried in hot air at a temperature of 105°C. Porous polyurethane sheets (sample 15.16) each having an apparent density of about 0.88 g/cm were obtained.

As a result of measuring the yellowing degree Δb of each of these samples, the yellowing degree Δb* of sample 15 made from the dispersion [IF] was 0.9.
The yellowing degree Δb* of Sample 16 made from dispersion [II] was 0.5, and it was a porous polyurethane sheet with excellent yellowing resistance.

[Effects of the Invention] The polyurethane product of the present invention has excellent yellowing resistance and resistance to yellowing and deterioration due to light deterioration and atmosphere, and is particularly suitable as a product for white goods or light-colored goods. be.

Claims (9)

[Claims] (1) A polyurethane product made of a polymer mainly composed of polyurethane elastomer, which has good yellowing resistance, characterized by the pH of the polyurethane constituting the product being in the range of 6.9 to 3.5. polyurethane products. (2) A polyurethane product with good yellowing resistance according to claim 1, wherein the polyurethane product contains an antioxidant and/or a light stabilizer. (3) The polyurethane product contains an antioxidant and/or a light stabilizer, and further contains an additive selected from a colorant, a filler, a softener, and a flame retardant. A polyurethane product with good yellowing resistance. (4) After solidifying the polymer by wet coagulating a polymer solution mainly composed of polyurethane elastomer in a non-solvent containing a polymer solvent, (a) washing the polymer, and (b) adjusting the pH of the polymer. A treatment step for adjusting the temperature to a range of 6.9 to 3.5, (
c) A method for producing a polyurethane product with good yellowing resistance, which is characterized by a combination of drying steps. (5) The method for producing a polyurethane product with good yellowing resistance according to claim 4, wherein the polymer mainly consisting of a polyurethane elastomer contains an antioxidant and/or a light stabilizer. (6) A patent claim in which a polymer mainly composed of polyurethane elastomer contains an antioxidant and/or a light stabilizer, and further contains an additive selected from a colorant, a filler, a softener, and a flame retardant. A method for producing a polyurethane product with good yellowing resistance according to item 4. (7) Claims 4 to 4, wherein the polymer solution mainly composed of polyurethane elastomer uses at least one selected from dimethylformamide, diethylformamide, dimethyl sulfoxide, and diethyl sulfoxide as a solvent. A method for producing a polyurethane product with good yellowing resistance according to any of item 6. (8) A polymer solution mainly composed of polyurethane elastomer is impregnated and/or applied to a fiber aggregate, and then wet coagulated in a non-solvent containing a polymer solvent to solidify the polymer. A method for producing a polyurethane product with good yellowing resistance according to any one of items 4 to 7. (9) A method for manufacturing polyurethane products in which a solution or dispersion of a polymer mainly composed of polyurethane elastomer is impregnated and/or applied to a fiber aggregate, and then the solvent or dispersant is evaporated to dry coagulate. pH 6.
After adjusting to a range of 9 to 3.5, nonionic or pH
A method for producing a polyurethane product with good yellowing resistance, which is used by dissolving or dispersing it in a solvent or dispersant having an acidic composition of 6.9 or less or an acidic composition adjusted to pH 6.9 or less.