JPH1181156A - Aqueous polyurethane-imparted artificial leather - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an artificial leather excellent in heat resistance and enabling to continuously dye an artificial leather raw fabric treated with an aqueous polyurethane resin for a long period and control the thermal decomposition of the dropped urethane resin on the dyeing, when the artificial leather raw fabric treated with the aqueous polyurethane resin is dyed by the use of a jet dyeing machine. SOLUTION: This artificial leather is obtained by imparting an aqueous polyurethane resin to a nonwoven fabric sheet having a single filament fineness of <=0.5 d, thermally drying the sheet and subsequently dyeing the obtained raw fabric. The aqueous polyurethane resin has an exothermic peak calorific value of <=50 mj/mg measured by a differential scanning calorimeter (DSC), an exothermic peak top temperature of >=215 deg.C, and an adhesive strength of <=700 g/cm between a polyurethane resin film and a stainless steel plate after a 180 deg.C dry thermal treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to artificial leather provided with water-based polyurethane. More specifically, when a nonwoven sheet-like material to which an aqueous polyurethane resin has been applied is dyed with a jet dyeing machine into artificial leather, the thermal decomposition of the urethane resin falling off during dyeing is suppressed, and the processing yield is improved and the dyeing machine is improved. To provide artificial leather with excellent heat resistance that enables long-term continuous operation.

[0002]

2. Description of the Related Art It is widely known that artificial polymers are obtained by applying various polymer compounds to a non-woven fabric mainly composed of ultrafine fibers and subjecting them to processing. The polymer compound in this case is soft and resilient as artificial leather, and has durability,
Polyurethane resins are often used to obtain physical properties such as dimensional stability.

Generally, a polyurethane resin is often applied to a non-woven fabric sheet as a solution dissolved in an organic solvent and wet-coagulated in many cases. However, the organic solvent used at that time is often a flammable and highly toxic substance, and much attention has to be paid to the recovery of the solvent in order to prevent the risk of fire and toxicity. Further, there is a disadvantage that the solvent is expensive and that the recovery from the dilute solution requires a large cost.

[0004] On the other hand, with the recent increasing interest in global environmental protection, the shift from organic solvent type to water-based polyurethane emulsion type has been receiving attention as a more ecological technology. However, many kinds of artificial leathers made of water-based polyurethane have a defect that many types of artificial leather cannot withstand the hot water rubbing action at 130 ° C. in the liquid jet dyeing, and the urethane resin easily falls off. There were drawbacks from the viewpoint of industrially stable production, such as clogging the strainer section and heat exchange section, or adhering to the vapor phase machine wall and severely contaminating the dyeing machine. This is considered to be because the aqueous polyurethane is polymerized by dispersion in water, and the molecular weight of the polymer is not as high as that of the solvent-based polymer, resulting in weak film formation and low heat resistance.

The present inventors have previously disclosed in Japanese Patent Application Laid-Open No. 07-2290.
In JP-A-71, as a method of reducing urethane resin falling off during dyeing and suppressing contamination of the falling urethane resin in a dyeing machine, the N, N
When the dissolution rate in N 'dimethylformamide is 12% or less,
Adhesive strength after dry heat treatment at 130 ° C is 1.2g / c
A method using an aqueous polyurethane emulsion of not more than m was completed, and an industrial mass production technology of artificial leather to which an aqueous polyurethane resin was applied was completed. However, as the operating rate of the dyeing machine has increased in response to production demands, the urethane waste accumulated in the jet dyeing machine has re-attached to the fabric due to thermal decomposition, and the reduction in processing yield has become a new problem. Have been.

Generally, a composite with a polyurethane resin is used.
When an artificial leather is subjected to liquid dyeing, about 10% or less of the polyurethane resin is dropped off by the dyeing cloth regardless of the solvent type or the aqueous type.
However, it can be said that the urethane is about 10%, but in the case of water-based polyurethane resin, the degree of polymerization is lower and the molecular weight distribution is wider than that of solvent-based polyurethane resin, so that the stability as a polymer is poor. And gradually caused thermal decomposition to cause coloration. At the same time, the ultra-fine fibers that have fallen out become microfilters, and the urethane resin that has decomposed in the process of micronizing the bubbles during dyeing aggregates to form sticky clumps, blocking the perforated plate of the heat exchanger. Or a phenomenon that a part of the lumps is torn off by the turbulent flow during the intense dyeing and reattached to the fabric occurs. For example, only a continuous operation for about one week is maintained, and the processing yield is as low as about 70%. Such as
Stable production was difficult. Furthermore, some of the resulting artificial leathers do not have sufficient performance for fields requiring high heat resistance, for example, for use in car seats.

[0007]

SUMMARY OF THE INVENTION The present invention suppresses the thermal decomposition of urethane resin dropped off during dyeing of an artificial leather raw material provided with an aqueous polyurethane resin with a liquid jet dyeing machine, thereby reducing the processing yield. An object of the present invention is to provide an artificial leather which is high in heat resistance and which can be continuously dyed for a long time.

[0008]

Means for Solving the Problems The present inventors have paid attention to the heat-resistant behavior of an aqueous polyurethane resin used to solve the above-mentioned problems caused by high-temperature liquid jet dyeing of artificial leather made of an aqueous polyurethane resin. However, as a result of intensive studies, the present invention has been reached. That is, the present invention relates to a differential scanning calorimeter (DS).
C) an aqueous polyurethane resin having a heating value of an exothermic peak generated in the course of heating up to 300 ° C. up to 300 ° C. of 50 mj / mg or less and a top temperature of the exothermic peak of 215 ° C. or more,
And the adhesive strength between the film made of the polyurethane resin and the stainless steel plate after the dry heat treatment at 180 ° C. is 700 g / cm.
The present invention relates to an artificial leather obtained by dyeing a nonwoven fabric sheet having a single yarn fineness of 0.5 d or less provided with an aqueous polyurethane resin as described below.

The more preferable range of the calorific value of the water-based polyurethane resin of the present invention is 40 mj / mg or less, the more preferable range is 30 mj / mg or less, and the top temperature of the exothermic peak is preferably 220 ° C. or more, more preferably 230 m / mg or more.
° C or higher. If the calorific value exceeds 50 mj / mg or the top temperature of the exothermic peak is less than 215 ° C., the above-mentioned severe problem occurs in the high-pressure liquid jet dyeing step, and not only stable production cannot be expected, but also Artificial leather is insufficient for fields requiring high heat resistance.

On the other hand, no exothermic peak is exhibited in the course of heating up to 300 ° C. by DSC, and the calorific value may be 0 mj / mg, and the water-based polyurethane resin excellent in heat stability in the present invention can be used. It is possible. In the present invention, the adhesive strength of the aqueous polyurethane resin film to the stainless steel plate is 700 g / cm or less, preferably 600 g / cm or less, and more preferably 400 g / cm or less. If the adhesive strength exceeds 700 g / cm, the dropped resin adheres to the walls of the dyeing machine and around the heat exchanger, and cannot be easily removed by disassembly and cleaning. Cause Of course, it does not show any adhesiveness to the stainless steel plate, that is, even if the adhesive strength is 0 g / cm, it does not hinder the use of the present invention at all, and the resin which has fallen into the dyeing machine can be easily removed. preferable.

[0011] The water-based polyurethane resin of the present invention comprises polyethylene adipate glycol as a polyol component,
Polyester diols such as polybutylene adipate glycol, polyether glycols such as polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetramethylene glycol (PTMG), and polycarbonate diol (PCG) can be used. Components include aromatic isocyanate (MDI) such as diphenylmethane-4,4'-diisocyanate, alicyclic isocyanate such as dicyclohexylmethane-4,4'-diisocyanate (H12-MDI), and fat such as hexamethylene isocyanate (HMDI). Aromatic diisocyanates can be used. As chain extenders, glycols such as ethylene glycol, ethylene diamines, diamines such as 4,4'-diaminodiphenylmethane, and trifunctional alcohols can be used. Such as alcohol and amine can be appropriately selected and used.

The polymerization method is not limited at all, as long as it satisfies the DSC behavior of the present invention, ie, the calorific value and the top temperature of the exothermic peak, and the adhesive strength range with stainless steel. Emulsion polymerization, ionization polymerization and the like are used. In the present invention, if necessary, an ultraviolet absorber, an antioxidant, a colorant, and the like can be added. As the preferable aqueous polyurethane resin of the present invention, a polyether-based non-yellowing polyurethane resin and a polycarbonate-based non-yellowing polyurethane resin are suitably used from the viewpoint of heat resistance, hot water resistance and light resistance, as described later.

Hereinafter, the present invention will be described in more detail using more specific embodiments. One method for obtaining the specific aqueous polyurethane of the present invention is to use an antioxidant as a heat resistance improver. The antioxidant can be added during the polymerization of the aqueous polyurethane, in the form of an emulsion after the completion of the polymerization, or in both steps. Since many antioxidants are powdery, it is difficult to uniformly add the antioxidant as it is, and therefore, a method of adding a predetermined amount in an aqueous solution in advance is desirable. Antioxidants are generally hindered amines, hindered phenols,
Hydrazine compounds are exemplified, and hindered amine compounds having a high molecular weight grade exhibit particularly excellent effects.

The change in the heat resistance of the aliphatic polyether-based water-based polyurethane resin in the case where "Cimasorb 944LD" (trade name: manufactured by Ciba Geigy) is added as a hindered amine-based antioxidant will be described. The decomposition calorific value as the DSC behavior of the resin film decreases almost linearly with the addition rate of the antioxidant (see FIG.
1). At the same time, the top temperature of the exothermic peak also rises (Figure 2)
However, a large improvement effect can be achieved. When a heat resistance evaluation was visually performed on a stainless steel plate of a film to which these antioxidants had been added, no decomposition coloring was observed at an addition rate of 1% by weight or more, but the antioxidation was measured by measuring the adhesiveness by the adhesive strength. It was found that it decreased almost linearly with the addition amount of the agent (FIG. 3). In obtaining the aqueous polyurethane resin of the present invention, the amount of the antioxidant added is in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight, more preferably 1 to 5% by weight based on the urethane resin solid content. % Range. If the amount of the antioxidant is less than 0.5% by weight, the effect of improving the heat resistance is insufficient. Further, even if it is added in excess of 10% by weight, the heat resistance is not further improved, and on the contrary, the liquid foams,
Undesirable adverse effects such as a reduction in feeling performance and an increase in cost are not preferred.

The antioxidant can be applied to polyester-based water-based polyurethanes. However, polyester-based ones usually have strong adhesiveness and have an adhesive strength to a stainless steel plate of 700.
It is necessary to be careful that the g / cm2 exceeds g / cm and adheres to the wall of the dyeing machine, and the dropped urethane easily adheres to the fabric. It is surprising that the improvement in heat resistance by the addition of an antioxidant suppresses the adverse effects caused by falling urethane due to high-temperature liquid-flow dyeing at 130 ° C., and contributes to an increase in the operation rate and processing yield of the dyeing machine.
In addition, the processing yield of the raw material during this period does not cause C generation due to the reattachment of urethane chips, and a high yield can be achieved. If a simple washing with caustic soda or sodium hydrosulfite is regularly incorporated between successive dyeings, the operating rate of the dyeing machine will be further improved. For example, when adding Timasorb 944LD to a polyether-based water-based polyurethane resin, the addition ratio is preferably 1% by weight based on the resin solid content.
The above conditions can be satisfied by the above addition.

Some of the antioxidants are liable to foam, and it is expected that troubles will occur due to foaming in a tank or bath in the process during use. For this,
It is effective to use a fatty acid ester-based defoamer in combination. Among the defoaming agents, silicone and mineral oils have a high defoaming effect, but care must be taken when using them because they promote the slip phenomenon between fibers in the nonwoven fabric. When a polycarbonate-based urethane is used as the water-based polyurethane of the present invention, the decomposition heat of decomposition of the DSC is 50 mj / mg or less and the top temperature of the exothermic peak easily reaches 215 ° C. or more even without using an antioxidant due to its polymer structure. Can be achieved. Moreover, the adhesive strength to the stainless steel plate is extremely low at 240 g / cm, and is extremely stable as a resin polymer without fear of adhering to the machine wall. Of course, it is also possible to use an antioxidant in combination.

The present invention is directed to a water-based polyurethane resin which can withstand 130 ° C. in wet flow at the time of jet dyeing. However, if the dyeing temperature is lower than 130 ° C., the heat resistance of the water-based polyurethane resin is not sufficient, and the operation of the dyeing machine is not sufficient. The rate can be further improved, and the processing yield can be as close as possible to 100%. As a material of the nonwoven fabric used in the present invention, polyester is preferable, but it is not limited to this and can be widely applied to general synthetic fibers.

The present invention is applied to a nonwoven fabric sheet made of ultrafine fibers of 0.5 d or less. With a fiber having a thickness exceeding 0.5 d, the texture of the nonwoven fabric is coarse and hard, and it is not possible to produce a soft and elegant artificial leather. In particular, in the case of suede-like artificial leather, an elegant lighting effect cannot be obtained and the commercial value is low. Other fibrous structures may be combined as long as the nonwoven fabric made of an ultrafine single fiber of 0.5 d or less is constituted as the surface layer. A conventionally known method is applied to the method of applying the polyurethane resin to the nonwoven fabric sheet, but a method of impregnating the nonwoven fabric sheet with an impregnation liquid containing the polyurethane resin is preferable.

The method for measuring physical properties according to the present invention is as follows. Heat value, top temperature: Differential scanning calorimeter (DSC, for example, DSC200 / TG / manufactured by SEIKO I & E)
Using DTA200), the sample weight is 5 to 10 mg, the temperature is raised to 300 ° C. by an air flow at a temperature rising rate of 10 ° C./min, and the expression peak is analyzed. The urethane resin film to be measured is prepared by coating a stock solution of the emulsion on a glass plate with a 0.75 mm applicator and drying at 25 ° C. for 20 hours at room temperature. Next, the film is put into a hot air dryer at 130 ° C. together with the glass plate and heat-treated for 20 minutes. Peel the polyurethane film from the glass plate, treat it in hot water at 130 ° C for 20 minutes, then treat it at 80 ° C for 15 minutes, wash it with water and air dry.

Adhesive strength: A 0.05 mm thick stainless steel plate (SUS30)
4) Place on top, treat with a hot air drier at 180 ° C for 20 minutes, cut the stainless plate together with 2cm width and measure the strength of the bonded surface with a tensile strength and elongation measuring machine. At this time, a tape or the like is attached to the urethane film to be peeled to stop the elongation of the film, so that the measurement accuracy is improved.

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. The operation of the liquid dyeing machine due to accumulation of debris in the machine was allowed up to 85% of the normal state at the maximum nozzle pressure, and the operation was stopped when the state was less than 85%. Further, the heat resistance of the product is such that the obtained artificial leather is heated at 110 ° C. for 1 hour.
The change in the texture before and after the heat treatment for 00 hours was evaluated with a cantilever, and those having a hardened texture due to the heat treatment were represented by x, and those having no change in the texture were represented by ○.

(Example 1) Polyester ultrafine fiber having a single fiber fineness of 0.15 d was produced by a direct spinning method, and the length was 5 mm.
After being cut into mm, the slurry was dispersed in water to prepare a papermaking slurry for the surface layer and the back layer. A gauze-like woven fabric made of 75d / 36f polyester fiber was inserted between the outer layer having a basis weight of 100 g / m ² and a back layer having a basis weight of 50 g / m ^2, and a three-layer laminated nonwoven fabric sheet was produced by continuous papermaking. Next, a three-dimensional entangled nonwoven fabric was obtained by injection of a high-speed water flow. The high-speed water flow was sprayed at a pressure of 40 kg / cm ² from the surface layer and at a pressure of 30 kg / cm ² from the back layer using a straight flow nozzle having a hole diameter of 0.1 mm. Next, the sheet was dried with a pin tenter to continuously produce a sheet having a basis weight of 200 g / m ² and a thickness of 0.8 mm. The surface layer of this sheet was buffed using # 400 emery paper at a paper speed of 1000 m / min. As an impregnating liquid, a polyether-based water-based polyurethane emulsion ("Evaphanol AP" manufactured by Nichika Chemical Co., Ltd.)
-12 ": An impregnating liquid comprising 9% by weight of a forced emulsification type nonionic solid content of 40%, an average particle size of 0.6 μm) and 3% by weight of sodium sulfate (Na ₂ SO ₄ ) as a heat-sensitive agent was prepared. As an antioxidant, "Cimasorb 944L
D "(manufactured by Ciba-Geigy) was prepared by adding 0.5, 1.0, and 3.0% by weight to the urethane resin solid content, respectively. After impregnating each of the liquids with the nonwoven fabric sheet, squeezing was performed using a mangle to adjust the adhesion rate so that the pickup rate became 120%. Thereafter, it was continuously heated and dried at 130 ° C. for 3 minutes with a pin tenter dryer to obtain an artificial leather raw material.

The artificial leather fabric was continuously dyed for 24 hours using a CUT-RA jet dyeing machine manufactured by Hisaka Seisakusho so that the bath ratio was 1:20 in an 800 liter bath. The dye is a disperse dye, which is dyed at 130 ° C for 20 minutes in a light-colored kettle with a concentration of 1 to 3% owf, and then reduced and washed with thiourea dioxide and caustic soda each at 3 g / liter at 80 ° C for 15 minutes. After acid neutralization, washing with water was one cycle. The raw material manufactured under the above conditions is continuously charged, and the condition of the dirt and clogging of the liquid jet dyeing machine is determined by keeping the maximum nozzle pressure at a retention rate of 85% from the normal state as a guide for continuous operation. Was. Thereafter, the dyeing machine was disassembled and cleaned to observe clogging of the heat exchange porous tube and stains around the rear hatch. When the amount of the antioxidant added was 3% by weight, no abnormality was found in the raw material after 4 weeks, but it was decomposed after 4 weeks in order to grasp the condition in the pot. Table 1 shows the obtained results.

[0024]

[Table 1]

The rate of occurrence of C-reaction due to falling urethane among C-reactions generated during the period was 70% without the antioxidant, but 0.5% by weight of the antioxidant was used. 30
%, 1.0% and 3.0% by weight, there was no occurrence of C anti-reflection due to the above cause. In addition, as a result of evaluating the heat resistance of each of the obtained artificial leathers, those without the addition of the antioxidant showed a hardening of the texture (heat resistance: x), and the artificial leather with the addition of 0.5% by weight of the antioxidant was added. Heat resistance of the leather: Δ, artificial leather to which 1% by weight and 3% by weight of an antioxidant were added, the heat resistance was ○.

(Example 2) A polycarbonate-based polyurethane emulsion ("Evaphanol AP C-55" manufactured by Nikka Chemical Co., Ltd .: non-ionic, forced emulsification type, solid content 40%, average particle size 0) was applied to the nonwoven fabric used in Example 1. 0.7 μm) to 9
Wt%, sodium sulfate (Na ₂ SO ₄ ) as heat sensitive agent
It was impregnated with an impregnation liquid consisting of 3% by weight. The mixture was squeezed with a mangle to adjust the peak-up rate to 120%, and continuously heated and dried at 130 ° C. for 3 minutes using a pin tenter dryer. The film performance of the urethane resin used was as shown in Table 2 below.

[0027]

[Table 2] This raw material was put into a liquid jet dyeing machine in the same manner as in Example 1, and continuous operation was confirmed, and continuous operation for 4 weeks could be achieved, and there was no generation of C counterpart due to urethane falling off during this period.
Extremely stable dyeing was possible, and the resulting artificial leather had a heat resistance of ○.

(Example 3) Same as Example 2 except that "Cimasorb 944LD" (manufactured by Ciba Geigy) was added as an antioxidant in an amount of 1.0% by weight based on the urethane resin solid content. A polycarbonate-based aqueous polyurethane emulsion impregnation liquid was prepared. In the same manner as in Example 2, the mixture was squeezed with a mangle and adjusted to a peak-up rate of 120%, and continuously dried by heating at 130 ° C. for 3 minutes using a pin tenter dryer. The film performance of the urethane resin used was as shown in Table 3 below.

[0029]

[Table 3] This raw material was put into a liquid jet dyeing machine in the same manner as in Example 1, and continuous operation was confirmed. Continuous operation for 4 weeks was achieved, and there was no generation of C-repelling due to urethane falling off during this period, which was extremely stable. The artificial leather thus obtained had a heat resistance of ○, and no hardening due to the heat treatment was observed.

[0030]

As described above, by applying a water-based polyurethane emulsion having heat resistance performance under specified conditions to a non-woven sheet material mainly composed of ultrafine fibers, the thermal decomposition of urethane resin dropped off during jet dyeing can be prevented. This enabled long-term continuous operation of the dyeing machine. As a result, artificial leather excellent in heat resistance was obtained, and the dyeing processing yield was greatly improved, thereby enabling stable industrial production of artificial leather.

[Brief description of the drawings]

FIG. 1 is a graph showing heat resistance performance of a resin film;
The relationship between the amount of the antioxidant added and the calorific value of DSC decomposition is shown.

FIG. 2 is a graph showing heat resistance performance of a resin film;
4 shows the relationship between the amount of the antioxidant added and the DSC peak temperature.

FIG. 3 is a graph showing heat resistance performance of a resin film;
The relationship between the amount of the antioxidant added and the adhesive strength to the stainless steel plate is shown.

Claims (1)

[Claims] 1. 300 by differential scanning calorimeter (DSC)
Exothermic peak at 50 ° C
j / mg or less, the top temperature of the exothermic peak is 215 ° C.
Nonwoven fabric having a single yarn fineness of 0.5 d or less provided with an aqueous polyurethane resin having the above-mentioned aqueous polyurethane resin and having an adhesive strength to a stainless steel plate of not more than 700 g / cm after a 180 ° C. dry heat treatment of a film made of the polyurethane resin. Artificial leather made by dyeing sheet materials.