JPS6322218B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyurethane composition that can provide artificial leather with excellent performance when used as enamel-like artificial leather. More specifically, when applied to the surface of artificial leather, it has excellent surface gloss and transparency, that is, enamel feeling, as well as bending resistance, especially low temperature bending resistance, light yellowing resistance, NOx gas yellowing resistance, surface physical properties, The present invention relates to a polyurethane composition capable of forming a surface coating layer with excellent heat and pressure resistance, and which can provide a glossy surface without trouble when forming the surface coating layer. Conventionally, as enamel-like artificial leather, a polyurethane layer with excellent transparency is provided on the surface of artificial leather.
Those with a glossy and smooth surface are used. Such enamel-like artificial leather is produced by applying a polyurethane solution to a smooth metal surface, then bonding the artificial leather, and removing the solvent from the polyurethane solution by evaporation, and then peeling it off from the metal surface. Generally used polyurethane has the disadvantage that it has poor peelability from metal surfaces and does not necessarily provide a smooth and glossy polyurethane layer. By increasing the amount of hard segments in polyurethane, a polyurethane with excellent metal releasability can be obtained, but in this case, the disadvantage is that the polyurethane is hard and has poor bending resistance. Furthermore, conventionally used polyurethane tends to yellow due to light or NOx gas, which greatly impairs the feel of the enamel. The present inventors conducted research on a polyurethane solution that satisfies all of these many required performances, and as a result, they arrived at the present invention. That is, the present invention is synthesized from a polymeric diol having an average molecular weight of 1500 to 3000, an alicyclic organic diisocyanate, and an alicyclic organic diamine, and under the following conditions (),
() and () () The polymeric diol is a mixed diol of (A) ethylene glycol-based polyester diol and/or polytetramethylene glycol, and (B) 1,6-hexanediol polycarbonate diol, and The mixing ratio of (A)/(B) is from 1/1 to 9/1 by weight; () At least one of the alicyclic organic diisocyanate and the alicyclic organic diamine is

[Formula] A polyurethane that satisfies the following: () The ratio of the alicyclic organic diisocyanate to the polymeric diol is 2.5 to 4.0 in molar ratio, and a solvent that dissolves this polyurethane. It is a polyurethane composition suitable for enamel-like artificial leather, characterized in that 40 to 85% by weight is tetrahydrofuran and 60 to 15% by weight is a compound whose main component is an alcohol-based compound. By using a polyurethane composition, it is possible to obtain an enamel layer that has excellent metal releasability, excellent transparency and surface gloss, and furthermore has excellent bending resistance and does not yellow due to light or NOx gas. Note that in the present invention,

[Formula] The compound having the group specifically refers to 3-isocyanatomethyl-
3,5,5-trimethylcyclohexyl isocyanate (commonly known as isoisophorone diisocyanate)
and 1-amino-3-aminomethyl-3,5,5
-trimethylcyclohexane (commonly known as isophoronediamine). Next, individual constituent elements of the present invention will be specifically explained. First, the polymeric diol, which is one of the raw materials used to synthesize polyurethane, which is one of the components of the polyurethane composition of the present invention, is
It is a mixture of ethylene glycol polyester diol and 1,6-hexanediol polycarbonate diol. Examples of the ethylene glycol-based polyester glycol include polyethylene adipate glycol (PEA), polyethylene butylene adipate glycol (PEBA), polyethylene hexylene adipate glycol (PEHA), and polyethylene propylene adipate glycol (PEPA). Ethylene glycol polyester diol (A) and 1,6
-Hexanediol polycarbonate glycol
The mixing ratio (A)/(B) of (B) is 1/1 to 9/1 by weight.
and preferably 6/4 to 9/1, and the average molecular weight of the polymeric diol must be in the range of 1,500 to 3,000. These conditions are particularly important in the present invention, and by satisfying these conditions, the metal releasability becomes good and the bending resistance, especially the low temperature bendability, becomes good. Outside the above mixing ratio range, either metal removability or bending resistance will be insufficient. Note that for applications requiring hydrolysis resistance, it is preferable to use polytetramethylene glycol instead of ethylene glycol-based polyester diol. Even when polytetramethylene glycol is used, a polyurethane with excellent metal releasability and bending resistance can be obtained. When using polytetramethylene glycol, the mixing ratio of polytetramethylene glycol/1,6-hexanediol polycarbonate diol is 1/1 to 9/1, preferably 6/4 to 8/1 by weight.
2, and the average molecular weight must be in the range of 1,500 to 3,000; if it is outside this range, the same disadvantages as mentioned above will occur. In the present invention, there is no problem in using a small amount of other polymeric polyols. Alicyclic organic diisocyanates used in the synthesis of polyurethane constituting the polyurethane composition of the present invention include isophorone diisocyanate,
Examples include dicyclohexylmethane-4,4'-diisocyanate and isopropylidenecyclohexane diisocyanate. Also, examples of the alicyclic organic diamines used in the synthesis of the polyurethane constituting the polyurethane composition of the present invention include isophorone diamine, 4,4'-diaminodicyclohexylmethane, cyclohexylene diamine, 4,4'-diamino-3,3' -dimethylcyclohexylmethane and the like. Enamel layers made of polyurethane obtained by using aliphatic organic diisocyanates and alicyclic organic diamines are significantly inferior in terms of heat resistance and physical properties; If used, it will be significantly inferior in terms of light yellowing resistance and NOx gas yellowing resistance. In the polyurethane composition of the present invention, as described above, at least one of the alicyclic organic diisocyanate and the alicyclic organic diamine used in the synthesis of the polyurethane is

It must be a compound with the group [Formula]. That is,
The alicyclic organic diisocyanate must be isophorone diisocyanate, the alicyclic diamine must be isophorone diamine, or both must be isophorone-based compounds. In particular, it is preferable to use isophorone diisocyanate and isophorone diamine in combination, and next, it is preferable to use dicyclohexylmethane-4,4'-diisocyanate and isophorone diamine in combination. In these cases, the resulting polyurethane has good solution stability in the solvent, that is, it rarely thickens over time or gels, and the enamel-like artificial product obtained using this polyurethane is The surface physical properties of the leather are improved, and the heat and pressure resistance is also improved. of course,
No yellowing due to light or NOx gas is observed. The molar ratio of the alicyclic organic diisocyanate to the polymeric diol must be 2.5 to 4.0, preferably 2.7 to 3.7. If it is less than 2.5, not only the metal removability will be poor, but also the heat pressure resistance and surface properties will be poor.
When it is 4.0 or more, metal peelability, heat pressure resistance, and surface physical properties are improved, but bending resistance, especially low-temperature flexibility, becomes extremely poor. In addition, in the polyurethane constituting the present invention, as the diisocyanate compound and the chain extender compound, compounds other than alicyclic compounds may be used in small amounts. The polyurethane constituting the polyurethane composition of the present invention is synthesized from the above-mentioned polymeric diol, alicyclic organic diisocyanate, and alicyclic organic diamine, and the method for synthesizing such a polyurethane is as follows: Various methods conventionally used for synthesizing polyurethane can be employed. The following are representative methods. First, a polymer diol and an alicyclic organic diisocyanate are heated to 50 to 130°C in a nitrogen atmosphere in a ratio such that the isocyanate group is in excess of the terminal hydroxyl group of the polymer diol, and the polymer diol is reacted with the terminal hydroxyl group. A polyurethane prepolymer having isocyanate groups is obtained. The obtained prepolymer is dissolved in a solvent, and the prepolymer is chain-extended with an alicyclic organic diamine at a temperature around room temperature to obtain a polyurethane solution. Next, the solvent, which is one of the components constituting the polyurethane composition of the present invention, must contain tetrahydrofuran as an essential component, and the amount thereof is 40 to 85% by weight, preferably 50 to 85% by weight of the total amount of the solvent. 70
Weight%. The remaining 60 to 15% by weight needs to be a compound whose main component is an alcoholic compound. Examples of alcoholic compounds include isopropanol, ethanol, methanol, ethyl cellosolve, methyl cellosolve, etc. Among them, it is particularly preferable to use isopropanol and methanol in combination in terms of solution stability. If the amount of tetrahydrofuran is less than 40% by weight,
If the amount exceeds 85% by weight, it will be difficult to ensure the solution stability of the polyurethane composition. Further, by making the remaining 60 to 15% by weight a compound whose main component is an alcoholic compound, solution stability can be obtained. Note that the term "compound containing an alcohol compound as a main component" means two types: a case where the compound consists only of an alcohol compound, and a case where a mixture of an alcohol compound and another compound is used. Other compounds used when alcohol-based compounds and other compounds are mixed are:
Examples include toluene, cyclohexanone, methyl ethyl ketone, and ethyl acetate. The solvent constituting the composition of the present invention may be the one used when synthesizing the polyurethane, or the solvent added to the polyurethane after the reaction. As mentioned above, from the polyurethane composition of the present invention, an enamel layer with excellent transparency and surface gloss, excellent metal releasability, and excellent bending resistance, light resistance, and NOx gas resistance can be obtained. Furthermore, the polyurethane composition itself has excellent solution stability. Therefore, it is extremely excellent as a resin solution for enamel. The present invention will be specifically explained below using Examples.
In the Examples, the enamel feel of the enamel-like artificial leather obtained using the polyurethane composition of the present invention was evaluated by visually judging the gloss and transparency. In addition, the bending resistance (20℃) and low-temperature flexibility (-20℃) are determined by the stroke width (maximum 3
The bending test was performed using a bending tester with a bending frequency of 8,600 times/hour (minimum time: 1 cm), and the number of bends until a slight scratch appeared was evaluated. Furthermore, the light yellowing resistance was measured using a fade meter when exposed to a carbon arc lamp in an atmosphere of 63°C for 200 hours.
In addition, NOx gas resistance is achieved at a NOx gas concentration of 150ppm.
This shows the discoloration after 48 hours of exposure. The surface properties are the results of observing the degree of surface wear when subjected to a Taber type abrasion tester with a load of 1 kg and 2000 friction times, and a fold abrasion tester (Custom type) with a load of 2 lb and 3000 friction times. When there is no scratch, it is marked with ○, when there is some damage, it is marked with △, and when there is damage to the extent that the substrate is visible, it is marked with ×. In addition, heat and pressure resistance determines whether the shoe can withstand the temperature and pressure conditions applied during shoe manufacturing. Specifically, the enamel texture is observed when the shoe is left at 100℃ for 1 hour under pressurized conditions. This is the result. A case where the gloss was lost and the enamel feel was greatly impaired was marked with an x, a case where the enamel feel was slightly impaired was marked with a △, and a case where the enamel feel was not impaired at all was marked with a mark of 0. Further, all the raw materials for polyurethane used in the examples are indicated using abbreviations, and the relationship between the abbreviations and the compounds is as follows.

[Table] Examples 1 to 6, Comparative Examples 1 to 8 Various polyurethane elastomers were manufactured from the polymer diols, organic diisocyanates, and chain extenders shown in Table 1. That is, a polymeric diol and an organic diisocyanate are reacted under nitrogen at 60 to 120°C for 5 to 10 hours with stirring, the resulting polyurethane prepolymer is dissolved in tetrahydrofuran, and then a predetermined amount of a chain extender is added to isopropanol and methanol. After dissolving in the polyurethane prepolymer at 30°C under a nitrogen atmosphere,
20% of polyurethane with a given viscosity (2000 centipoise) was reacted with stirring for 5 hours.
A weight percent solution was obtained. The solvent composition at this time was tetrahydrofuran:isopropanol:methanol=65:21:14 (weight ratio). Next, the obtained polyurethane solution is applied onto the metal belt so that the film thickness of the solid content is 25 microns on average, and on top of that, a porous layer of polyurethane is formed on the surface of the polyurethane-impregnated nylon entangled nonwoven fabric. A non-porous polyurethane layer is formed on the surface of the artificial leather, and in this state, the solvent of the solution is completely evaporated at a drying temperature of 45 to 100°C, and then it is peeled off from the metal belt and the enamel is removed. Obtained artificial leather. The obtained enamel-like artificial leather was subjected to various tests. The results are shown in Table 2. In addition, Comparative Example 1 is based on the prerequisites () specified in the present invention and when no alicyclic diamine is used,
Comparative Examples 2, 5, and 6 are when requirement () is not used, Comparative Example 3 is when requirement (), alicyclic diisocyanate and alicyclic diamine are not used, and Comparative Example 4 is when requirement () and alicyclic diisocyanate are not used. If not used, Comparative Examples 7 and 8 meet the requirements ()
This is the case when you do not use .

【table】

[Table] Comparative Example 9 The polyurethane solvent used in Example 1 was replaced with a mixture of isopropanol and toluene (mixing ratio 1:
When a polyurethane solution prepared using this solvent was used instead of 1) as an enamel layer of artificial leather in the same manner as in the above example, the enamel feel was clearly inferior.

Claims (1)

[Scope of Claims] 1 Synthesized from a polymeric diol having an average molecular weight of 1500 to 3000, an alicyclic organic diisocyanate, and an alicyclic organic diamine, and under the following conditions (),
() and () () The polymeric diol is a mixed diol of (A) ethylene glycol-based polyester diol and/or polytetramethylene glycol, and (B) 1,6-hexanediol polycarbonate diol, and The mixing ratio of (A)/(B) is from 1/1 to 9/1 by weight; () At least one of the alicyclic organic diisocyanate and the alicyclic organic diamine is
[Formula] A polyurethane that satisfies the following: () The ratio of the alicyclic organic diisocyanate to the polymeric diol is 2.5 to 4.0 in molar ratio, and a solvent that dissolves this polyurethane. A polyurethane composition suitable for enamel-like artificial leather, characterized in that 40 to 85% by weight is tetrahydrofuran and 60 to 15% by weight is a compound whose main component is an alcoholic compound.