CN1170030C

CN1170030C - Method for manufacturing polyurethane synthetic leather

Info

Publication number: CN1170030C
Application number: CNB991093887A
Authority: CN
Inventors: 陈龙腾; 蔡梵正; 张年喜
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 1999-06-29
Filing date: 1999-06-29
Publication date: 2004-10-06
Anticipated expiration: 2019-06-29
Also published as: CN1279313A

Abstract

The invention relates to a method for manufacturing a poly helium ester synthetic leather. And (3) taking moisture-cured polyurethane as an adhesive layer, and adhering the polyurethane film layer on the substrate layer to prepare a synthetic leather finished product. The moisture hardening polyurethane absorbs moisture and then hardens to achieve the effects of sticking and bonding. The raw material source of the polyurethane coating layer can be (I) granular hot-melt type polyurethane, (II) ultraviolet hardening polyurethane, (III) single-solvent type polyurethane, (IV) water-based polyurethane, (V) moisture hardening polyurethane or (VI) traditional multi-solvent type polyurethane. The invention provides a method for preparing polyurethane synthetic leather with low pollution degree, high production rate and low cost.

Description

Method for manufacturing polyurethane synthetic leather

The invention relates to a method for manufacturing polyurethane synthetic leather, in particular to a method for manufacturing polyurethane synthetic leather by using moisture-cured polyurethane as an adhesive layer to adhere a polyurethane film layer to a substrate layer.

The production of synthetic leather has been in the past for many years and is widely used in the civil industry, such as leather bags, leather clothing, leather decorations, sports shoes and the like, and the method for producing the synthetic leather is described in detail in the handbook of polyurethane resin (published by journal industry news agency). In recent years, various patents have focused on the improvement of functionality, such as air permeability, fire resistance, patterns, or color appearance. For example: the Nippon Dongli company adds calcium carbonate and phosphide into polyurethane to produce synthetic leather with good air and moisture permeability (JP-49008507). Kato et al produced artificial leather having excellent flexibility using fine fibers and polyurethane (US 4,612,228), Dongli produced synthetic leather having self-extinguishing function using acrylic polymer, halogen phosphate and polyurethane (JP-58013786), and Dongli produced synthetic leather havingthree-dimensional pattern using vinyl hexene acrylic fibers and polyurethane (EP 98604).

The polyurethane Binder (Binder) used in the above patents is mostly liquid polyurethane containing solvent, and has a disadvantage that the solvent is evaporated to release a large amount of solvent during the production of synthetic leather, resulting in contamination. Kiren et al heat and melt granular PU, and then make the artificial leather (JP60099078) suitable for hand bags with non-woven fabric, but the polyurethane used does not have moisture hardening function.

DE-19504007 describes the production of moisture-curing polyurethane hotmelt adhesives from isocyanates (MDI) and polyols for bonding fibrous materials, such as synthetic leather and textiles, with emphasis on producing PU hotmelt adhesives, without disclosing synthetic leather production techniques.

Comstock et al have produced moisture-hardening coatings with polyester polyols and isocyanates, which have high abrasion resistance of the coating film, but have not disclosed the related art for producing synthetic skins (Amer. Ass. text. chem. color. Symp. 1973).

The manufacturing process of the conventional polyurethane synthetic leather is shown in fig. 1. First, a release paper 101 wound on a roll 10 is conveyed to an oven 13 through rolls 11, 12, a solution of polyurethane is coated on the release paper 101 through a doctor blade 103 at the roll 12 to form a skin layer, the polyurethane-coated release paper 102 is conveyed to the oven 13 to be baked to remove the solvent, the dried skin layer is conveyed to a cooling roller 14 again to be cooled and then conveyed to a coating wheel 15, a two-liquid type resin mixed solution containing the solvent is pasted on the skin layer through a doctor blade 105 at the coating wheel 15 to be coated thereon, and a base material 106 wound on the roll is pasted on the skin layer through a lamination roller 16, dried through an oven 17, cooled through a cooling roller 18 and wound into a synthetic skin product 19. Wherein the base material 106 includes a base cloth, a split leather, a wet leather, and the like.

As shown in the flow chart of fig. 1, waste gases such as Dimethylformamide (DMF), Methyl Ethyl Ketone (MEK), Ethyl Acetate (EAC) and toluene are generated in the steps of coating, drying to form a film, pasting, bonding and drying, which may cause serious environmental pollution. On average, 300 grams of solvent is discharged to the atmosphere for every yard of synthetic leather manufactured.

In order to overcome the disadvantages of the polyurethane synthetic leather, a single solvent type polyurethane synthetic leather process is actively promoted in the industry in recent years. The process only uses DMF single solvent, so the pollution of waste gas is less serious, however, in order to use DMF single solvent, special polyurethane is required to be selected as adhesive, the adhesive in the process needs DMF as solvent, and the defect of polluting environment still exists. Moreover, the boiling point of DMF solvent is as high as 150 ℃, the production rate is slow, so the production line needs to be longer than the traditional dry process, the cost is increased, and the energy is wasted.

In view of the above disadvantages of the conventional polyurethane synthetic leather manufacturing method and the manufacturing method of single solvent type polyurethane synthetic leather, the present invention provides a manufacturing method of polyurethane synthetic leather with low pollution, high production rate and low cost.

In order to achieve the above object, the method for producing polyurethane synthetic leather of the present invention comprises the steps of respectively producing leather layers, wherein the types of the leather layers are six: particle hot melt polyurethane, (II) ultraviolet hardening polyurethane, (III) single solvent polyurethane, (IV) aqueous polyurethane, (V) moisture hardening polyurethane and (VI) traditional multi-solvent polyurethane. And then, one of the six leather coating layers is respectively attached to the base material layer by using moisture-cured polyurethane as an adhesive. The moisture hardening polyurethane used as the bonding layer is solid at room temperature, needs to be heated and melted by a hot melting machine, is coated on the leather film layer, and is then attached to the base material layer to complete the manufacturing of the synthetic leather. And (3) placing the synthetic leather finished product in the atmosphere, and forming the polyurethane synthetic leather after the isocyanate functional group in the moisture-cured polyurethane prepolymer and the moisture in the air react. The process for manufacturing the moisture-hardening polyurethane synthetic leather can also melt the moisture-hardening polyurethane, then coat the moisture-hardening polyurethane on the substrate layer, and then attach the leather layer to finish the manufacturing of the synthetic leather.

Because the adhesive does not need to use a solvent when the film layer is adhered to the substrate layer according to the preparation method of the invention, the pollution to the air can be greatly reduced. Moreover, because no solvent is used, the drying step of evaporating the solvent can be reduced, thereby accelerating the production rate and reducing the production cost.

The present invention will be described in detail below with reference to the accompanying drawings and examples.

The drawings are briefly described as follows:

FIG. 1 is a flow chart of the production of a conventional polyurethane synthetic leather;

FIG. 2 is a flow chart of a method of manufacturing a substrate layer by coating a conventional multi-solvent polyurethane, single-solvent polyurethane, or waterborne polyurethane as a coating layer and a moisture-curable polyurethane as a bonding layer on the coating layer in accordance with the present invention;

FIG. 3 is a flow chart of a method of making a skin layer using moisture-curable polyurethane and an adhesive layer using moisture-curable polyurethane in accordance with the present invention;

FIG. 4 is a flow chart of a method of making a cover layer using UV-curable polyurethane and an adhesive layer using moisture-curable polyurethane in accordance with the present invention;

FIG. 5 is a flow chart of a method of making a film using a granular hot melt polyurethane as a coating layer and a moisture curing polyurethane as an adhesive layer in accordance with the present invention;

fig. 6 is a flow chart of a method of manufacturing a substrate using conventional multi-solvent polyurethane, single-solvent polyurethane, or waterborne polyurethane as a coating layer and moisture-curable polyurethane as an adhesive layer, but with the adhesive applied to the substrate layer and then bonded to the coating layer, in accordance with the present invention.

The invention relates to a method for manufacturing polyurethane synthetic leather, which comprises the following steps:

(a) forming a polyurethane skin layer, the polyurethane being selected from the group consisting of particulate hot melt polyurethane, ultraviolet curable polyurethane, conventional multi-solvent polyurethane, single solvent polyurethane, waterborne polyurethane, and moisture curable polyurethane;

(b) coating the moisture-hardening polyurethane prepolymer on the skin layer or the substrate layer as an adhesive layer, and

(c) and adhering a substrate layer or a coating layer on the adhesive layer.

In the method of the present invention, step (a) comprises applying the polyurethane on the release paper or release film by roll coating, spray coating, curtain coating, impregnation or doctor blade coating, preferably by doctor blade coating; wherein, the step (a) also comprises diluting single-solvent type or multi-solvent type polyurethane or waterborne polyurethane into a solution with the fixed content of 10-30wt percent, coating the solution on release paper or release film, and drying; wherein, the step (a) also comprises the steps of heating and melting the solid moisture hardening polyurethane or the particle hot melt polyurethane and then coating the solid moisture hardening polyurethane or the particle hot melt polyurethane on release paper or release film; wherein the step (a) further comprises coating the ultraviolet-curing polyurethane on release paper or release film, and polymerizing the ultraviolet-curing polyurethane by irradiation of ultraviolet rays to form a skin film layer.

According to the preparation method of the invention, a polyurethane film layer is formed firstly. The method for forming the polyurethane film layer is to coat the polyurethane on release paper or release film. The suitable release paper or release film can be high temperature resistant, medium temperature resistant and low temperature resistant. For example, a polyethylene and silicone release agent are coated on kraft paper, a silicone release agent is coated on strengthened kraft paper or grey paper, and a silicone-containing release agent is coated on a plastic film. For example, in the case of multi-solvent polyurethane, single-solvent polyurethane and aqueous polyurethane, the polyurethane can be dissolved in a suitable solvent to be diluted into a solution containing 10-30 wt% of solids, and then the solution can be coated on release paper or release film. The coating viscosity is preferably 1000-3000 Centipoise (CPS), and the coating thickness is preferably 0.02mm to 0.3 mm. The coating method can be knife roll coating, spray coating, curtain coating, impregnation, etc. Among them, the doctor blade roll coating method is preferred. When the polyurethane is granular hot-melt polyurethane or moisture-hardening polyurethane, the polyurethane is heated and melted and then directly coated on release paper or release film to form a skin film layer.

When multi-solvent polyurethane, single-solvent polyurethane or aqueous polyurethane is used as the skin layer, the polyurethane is dried after being coated on release paper or release film, usually two-stage dried in an oven at about 60-100 ℃ and about 120-160 ℃ for 1-10 minutes, and then cooled to be sent to the next step for coating the adhesive layer. And if moisture-hardening polyurethane or particle hot-melt polyurethane is used, the polyurethane is cooled to form a film and then sent to the next step for coating the adhesive.

In the method of the present invention, wherein the step (b) comprises melting the solid moisture-hardening polyurethane and then directly coating the solid moisture-hardening polyurethane on the skin layer or the substrate layer. The coating method can be roll coating, spray coating, curtain coating, impregnation or doctor blade coating, wherein the spray coating method is preferred, the coating temperature is 100-.

The chemical reaction principle of the moisture-hardening polyurethane in the adhesive layer is that the moisture-hardening polyurethane has an NCO group at the end, and when contacted withan active hydrogen-containing compound such as water, ammonia, alcohol, etc., a bridging structure is formed and hardened. For example, contact with moisture in the air will produce the following reaction:

(1) reacting with water to form amines

(2) With amines to produce urea

(3) React with urea to form a bridging structure

The reactions (1), (2) and (3) are actually carried out continuously, and then the hardening is completed.

In the method of the present invention, the step (c) is to adhere a substrate layer or a coating layer to the adhesive layer. Suitable substrate layers can be base fabrics such as industrial fabrics, nylon fabrics, woven nonwovens, knitted nonwovens, microfiber fabrics, dry synthetic leather or wet synthetic leather such as polyurethane synthetic leather, PVC leather, Erlang leather, animal leather such as cow leather, pig leather, sheep leather, and the like, or release paper. The mode of adhering the substrate layer can be a roller rolling mode, and the release paper is peeled after cooling to obtain the polyurethane synthetic leather.

In the method for manufacturing the polyurethane synthetic leather, the step (c) comprises the steps of rolling the leather film layer and the substrate layer by a lamination roller;

because the bonding layer used by the invention is moisture-cured polyurethane, the prepared polyurethane synthetic leather can be naturally cured after standing for 1-72 hours at room temperature, and the leather film layer and the substrate layer are firmly adhered to form the synthetic leather. If the hardening of the adhesive layer is to be accelerated, the hardening can also be accelerated by a steam bath or a steam method including derivatives of ammonia.

The method for manufacturing the polyurethane synthetic leather further comprises the step (d) of hardening the substrate layer adhered with the leather layer in a steam bath or a steam bath containing an ammonia derivative.

Referring now to fig. 2, fig. 2 is a schematic view of the method of the present invention for manufacturing a polyurethane synthetic leather using aqueous polyurethane, single solvent polyurethane or conventional multi-solvent polyurethane as a raw material of a leather layer. The release paper 201 wound on a roller 20 is first conveyed to an oven 23 through

rollers

21 and 22, at the roller 22, the release paper 201 is coated with water-based polyurethane or single solvent polyurethane or traditional multi-solvent polyurethane dissolved into solution by a scraper 204 to form a skin film layer, the release paper 202 coated with polyurethane is sent to the oven for drying, then sent to a coating wheel 25 after being cooled and rolled by a cooling roller 24, at the coating wheel 25, moisture-hardened polyurethane is coated on the skin film layer through the scraper 205, and a base cloth 29 wound on a roller 27 is attached on the moisture-hardened polyurethane layer through a lamination roller 26 and then wound to form a product 28.

Referring to fig. 3, fig. 3 is a schematic view of the method of the present invention for manufacturing polyurethane synthetic leather by using moisture-hardening polyurethane as a raw material of a leather layer. First, a release paper 301 wound around a roll 30 is fed through

rolls

31, 32, moisture-hardening polyurethane melted at the roll 32 is coated on the release paper 301 by a doctorblade 303 to form a skin layer, the polyurethane-coated release paper 302 is sprayed with water vapor by a sprayer 304 and fed to a coating wheel 34 through a roller 33, the moisture-hardening polyurethane is coated on the skin layer by a doctor blade 305 at the coating wheel 34, and a base cloth 37 wound around a roll 36 is attached on the moisture-hardening polyurethane by a lamination roller 35 and wound to form a product 38.

Referring to fig. 4, fig. 4 is a schematic view of the method of the present invention for manufacturing polyurethane synthetic leather by using ultraviolet-curable polyurethane as a raw material of a leather layer. First, a release paper 401 wound around a roll 40 is conveyed through

rolls

41, 42, an ultraviolet-curable polyurethane at the roll 42 is coated on the release paper 401 by a doctor blade 403 to form a skin layer, the polyurethane-coated release paper 402 is irradiated by an ultraviolet lamp 404 and conveyed to a coating wheel 44 through a roll 43, a moisture-curable polyurethane is coated on the skin layer at the coating wheel 44 by a doctor blade 405, and a base cloth 47 wound around a roll 46 is attached to the moisture-curable polyurethane through a lamination roll 45 and is wound to form a product 48.

Referring to fig. 5, fig. 5 is a schematic view of the method of the present invention for manufacturing polyurethane synthetic leather using particle hot melt polyurethane as a raw material of a leather layer. First, a release paper 501 wound around a roll 50 is fed through

rolls

51, 52, a granular hot-melt polyurethane melted at the roll 52 is coated on the release paper 501 with a doctor blade 503 to form a skin layer, the polyurethane-coated release paper 502 is fed to a coating wheel 54 through a roll 53, a moisture-hardening polyurethane is coated on the skin layer at the coating wheel 54 through a doctor blade 505, and a base fabric 57 wound around a roll 56 is attached to the moisture-hardening polyurethane through a lamination roll 55 and then wound to form a product 58.

Referring now to fig. 6, fig. 6 is a schematic view of the method of the present invention for manufacturing a polyurethane synthetic leather using conventional multi-solvent polyurethane, aqueous polyurethane or single-solvent polyurethane as a raw material of a skin layer, but a moisture-hardening polyurethane adhesive layer is coated on a substrate layer. Firstly, the release paper 601 wound on a roller 60 is conveyed to an oven 63 through rollers 61 and 62, at the roller 62, the water-based polyurethane or single solvent polyurethane or traditional multi-solvent polyurethane dissolved into solution is coated on the release paper 601 by a scraper 604 to form a skin film layer, and the release paper 602 coated with polyurethane is sent to the oven for drying, then is sent to a lamination roller 66 after being cooled and rolled by a cooling roller 64. On the other hand, the base fabric 69 wound on the roll 67 is sent to the coating wheel 65, at the coating wheel 65, the moisture-hardening polyurethane is coated on the base fabric 69 via the blade 605, and is converged and laminated via the laminating roller 66 with the polyurethane-coated release paper 602 simultaneously sent to the laminating roller 66, and is wound into the product 68.

The present invention is described in detail by the following examples, which are merely illustrative of the process of the present invention and are not intended to limit the scope of the present invention.

Example 1:

polyurethane synthetic leather was manufactured by the apparatus shown in FIG. 2. First, a single solvent polyurethane (NOVOTEX, Italy, model S-650) was diluted with DMF to a fixed content of 18 wt%. Then, the one-solvent polyurethane was applied to a release paper with a doctor blade (knife coater) to a dry film thickness of 18 stripes (0.18mm), and dried at 80 ℃ and 140 ℃ for 1 minute, respectively. The moisture-curing polyurethane is then heated in a moisture-insulated state with a hotplate (heater) to a liquid polyurethane at 150 ℃. After the single solvent polyurethane forms a film, coating liquid moisture hardening polyurethane (American H.B.Fuller product, model NP-2114T) on a single solvent polyurethane film layer, wherein the thickness of the film is 10 (0.1mm), sticking wet polyurethane synthetic leather by a rolling wheel, cooling, peeling off release paper, and standing for 2 hours at room temperature to obtain the polyurethane synthetic leather.

Example 2:

polyurethane synthetic leather was manufactured by the apparatus shown in FIG. 2. The single solvent polyurethane was first diluted with DMF to a fixed content of 18 wt% solution. Thereafter, the one-solvent polyurethane was applied to a release paper with a dry film thickness of 10 stripes (0.1mm) by means of a doctor blade (knifecoater), and dried at 80 ℃ and 140 ℃ for 1 minute, respectively. The moisture-curing polyurethane is then heated in a moisture-insulated state with a hotplate (heater) to a liquid polyurethane at 150 ℃. After the single solvent polyurethane forms a film, coating the liquid moisture hardening polyurethane on the single solvent polyurethane film with the thickness of 10 strips (0.1mm), sticking the wet polyurethane synthetic leather on a rolling wheel, cooling, stripping release paper, and standing for 2 hours at room temperature to obtain the polyurethane synthetic leather.

Example 3:

polyurethane synthetic leather was manufactured by the apparatus shown in FIG. 2. First, a conventional multi-solvent type polyurethane (model S-3030, manufactured by Takara Shuzo Co., Ltd.) containing DMF, MEK, toluene, EAC, etc. was diluted with a solvent toprepare a solution having a fixed content of 20 wt%. The multi-solvent polyurethane was applied to a release paper with a doctor blade (knifecoater) to a dry film thickness of 18 strips (0.18mm) and dried at 80 ℃ and 140 ℃ for 1 minute, respectively. The moisture-curing polyurethane is then heated with a hot plate (heater) to a liquid polyurethane at 150 ℃. After the traditional multi-solvent polyurethane forms a leather film layer, coating moisture-hardening polyurethane on the leather film layer, wherein the thickness of the moisture-hardening polyurethane is 10 strips (0.1mm), then sticking a wet polyurethane synthetic leather on a rolling wheel, cooling, stripping release paper, and standing for 2 hours at room temperature to obtain the polyurethane synthetic leather.

Example 4:

polyurethane synthetic leather was manufactured by the apparatus shown in FIG. 3. After the moisture-curing polyurethane was first heated to 150 ℃ liquid polyurethane with a hot plate (heater) in a moisture-blocking state, the moisture-curing polyurethane was coated on a release paper with a knife coater to a dry film thickness of 18 tapes. After moisture hardening polyurethane forms a skin film layer, liquid moisture hardening polyurethane is coated on the moisture hardening polyurethane film, the thickness of the moisture hardening polyurethane film is 10 strips (0.1mm), a rolling wheel is used for attaching the wet polyurethane synthetic skin, after cooling, release paper is peeled off, and the wet polyurethane synthetic skin is kept still for 2 hours at room temperature, so that the polyurethane synthetic skin is prepared.

Claims

1. a manufacture method of polyurethane synthetic leather, it may further comprise the steps:

(a) forming a polyurethane film layer, the polyurethane is selected from granular hot-melt polyurethane, ultraviolet curing polyurethane, multi-solvent polyurethane, single solvent polyurethane, water-based polyurethane or moisture-curing polyurethane;

(b) coating moisture-curing polyurethane on the skin layer or substrate layer as an adhesive layer, and

(c) Adhere the substrate layer or the film layer to the adhesive layer.

2. The manufacture method of polyurethane synthetic leather according to claim 1, wherein (a) step comprises that described polyurethane is coated on release paper or release paper with the method of roll coating, spray coating, flow coating, dipping or coating doctor blade. type film.

3. The manufacture method of polyurethane synthetic leather according to claim 2, wherein (a) step comprises coating above-mentioned polyurethane on release paper or release film in the mode of coating a doctor blade.

4. The manufacture method of polyurethane synthetic leather according to claim 2, wherein (a) step comprises multi-solvent type polyurethane, or single solvent type polyurethane or water-based polyurethane are diluted to a fixed content of 10-30wt% in a suitable solvent Solution, and then coated on the release paper or film.

5. The method for producing polyurethane synthetic leather according to claim 4, wherein the coating viscosity is 1000-3000 centipoise, and the coating thickness is 0.02mm-0.3mm.

6. The method for producing polyurethane synthetic leather according to claim 4, further comprising drying in two stages at a temperature of 60-100°C and 120-160°C for 1-10 minutes and then cooling.

7. The manufacture method of polyurethane synthetic leather according to claim 2, wherein (a) step comprises coating on the release paper or the release film after heating and melting the particle hot-melt polyurethane or moisture hardening polyurethane.

8. The manufacture method of polyurethane synthetic leather according to claim 2, wherein (a) step comprises coating ultraviolet curable polyurethane on release paper or release film and irradiating with ultraviolet rays.

9. The manufacture method of polyurethane synthetic leather according to claim 1, wherein the release paper or release film is high temperature resistant type or medium temperature resistant type or low temperature resistant type paper.

10. The manufacture method of polyurethane synthetic leather according to claim 9, wherein the release paper or release film is selected from coating polyethylene and silicone release agent on kraft paper, and coating silicone on kraft paper or lime paper Release agent or silicone release agent on plastic film.

11. The method for producing polyurethane synthetic leather according to claim 1, wherein (b) step comprises melting the solid moisture-curing polyurethane and coating it on the surface by rolling, spraying, flow coating, dipping or coating with a doctor blade. On the skin layer or substrate layer.

12. The method for producing polyurethane synthetic leather according to claim 11, wherein the coating temperature is 100-180° C., the coating viscosity is 3000-50000 centipoise, and the coating thickness is 0.02 mm-0.3 mm.

13. The manufacturing method of polyurethane synthetic leather according to claim 11, wherein the base material is selected from base cloth, animal skin, wet synthetic leather, dry synthetic leather, PVC leather, two palm leather or release paper.

14. The manufacturing method of polyurethane synthetic leather according to claim 13, wherein the base cloth is selected from industrial cloth, nylon cloth, water-woven non-woven cloth, knitted non-woven cloth or microfiber cloth.

15. The manufacturing method of polyurethane synthetic leather according to claim 1, wherein the step (c) comprises rolling the skin film layer and the base material layer with a lamination roller.

16. The method for producing polyurethane synthetic leather according to claim 1, further comprising (d) a step of hardening the substrate layer adhered with the film layer in a steam bath or a steam bath containing ammonia derivatives.