A spray-free polyurethane self-skinning foam and method of making the same

Abstract

The application discloses a kind of spray-free polyurethane self-skinning foam material and its preparation method.Polyurethane self-skinning foam material includes A material and B material is prepared using closed mold pouring process.By adjusting the ratio of grafted polyether and trifunctional polyether in A material and the specific proportion of color paste, the requirement of surface defect-free is met, the light and aging resistance requirement after various non-spray painting is met by adding aging aid, the friction resistance requirement is met by using physical blowing agent and low surface energy particles, and the polyurethane foam produced under the condition of non-spray painting can meet various requirements that can only be met by spray-painted foam, such as excellent appearance, comfortable hand feeling, good light resistance and friction resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polyurethane materials, and particularly relates to a spray-free in-mold paint polyurethane self-skinning foam material and a preparation method thereof, in particular to a spray-free polyurethane self-skinning foam material containing a specific grafting polyether component ratio and low surface energy particles and a preparation method thereof. BACKGROUND

[0002] Polyurethane self-skinning foam is widely loved by consumers and production enterprises due to the advantage of being able to form a skin material and a core material at one time, and is thus widely used in automobile steering wheels, engine covers, bicycle saddles, shoe materials, sports goods, home handrails and seats, etc. However, in the production process, in-mold paint is usually sprayed to cover the color difference and pinhole defects on the surface of the polyurethane foam, to avoid yellowing of the foam and affect the appearance of the foam product, to improve the gloss of the surface to beautify the appearance, and to improve the hand feeling. The in-mold paint is usually obtained by the reaction of polyester and aliphatic isocyanate, and this material has the characteristics of wear resistance and light insensitivity, so the polyurethane foam sprayed with in-mold paint also has good wear resistance and light resistance.

[0003] However, this process of spraying in-mold paint has many disadvantages, mainly including pollution (including to the environment and the foam product itself), increased carbon emissions, affecting the health of workers, rising production material costs and time costs, etc. In terms of pollution, the paint mist formed by spraying paint contains a large amount of organic pollutants such as benzene, styrene, toluene, formaldehyde, acetaldehyde, etc., which will have serious negative effects on the environment, the health of workers and the VOC performance of the foam, so in order to meet environmental protection requirements, factories need to spend a lot of money on waste gas treatment every year, workers need to wear gas masks and masks to prevent inhaling pollutants, and the VOC test of the foam often shows unqualified results. For the production of self-skinning foam, the in-mold paint is expensive, and the spraying of in-mold paint in production requires time, and often causes problems such as increased scrap rate due to improper operation of workers, etc.

[0004] If in-mold paint is not sprayed in the existing production of self-skinning foam, the foam surface is dull and has serious color difference, is covered with large and small pinholes, and the appearance cannot meet the factory requirements; the self-skinning formed by full-water polyurethane foaming is too thin to meet the wear resistance requirements; the isocyanate used in common polyurethane products is aromatic isocyanate, which easily yellow when exposed to light, and cannot meet the light resistance requirements, and the color changes significantly in a short time after leaving the factory.

[0005] Patent CN101597370B discloses a preparation method of water foaming self-skin polyurethane composition, which adjusts polyether component and modifies isocyanate and uses water as foaming agent, so that the self-skin foam product which meets the requirements of environmental protection and can be quickly demoulded is obtained, but the patent does not solve the problems of pinholes and color difference on the foam surface. Patent CN102140163A obtains similar physical properties to physical foaming by reasonable collocation of small molecule diols, modification of various isocyanates and water foaming, and the surface is smooth and the skin is clear. However, the patent also does not solve the problems of insufficient skin density and difficult-to-meet wear resistance. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, provide a spray-free polyurethane self-skin material and a preparation method thereof, from A material, a large amount of grafted polyether polyol is used to improve the opening of the foam to eliminate the pinholes on the foam surface, a specific amount of color paste is used to avoid surface color difference, and an anti-aging agent is added to meet the light resistance and aging requirements, from B material, a proper amount of polymeric and modified isocyanate is introduced, and a physical foaming agent is used, low surface energy particles are added and the use of a foaming catalyst is avoided to improve the wear resistance of the foam surface, and finally a polyurethane self-skin foam material which can meet the requirements of wear resistance, yellowing and other conventional performance requirements and production process requirements is obtained. The problems caused by the need for paint spraying of the existing polyurethane self-skin foam are solved, and the appearance, light resistance and wear resistance problems of the polyurethane self-skin foam material without paint spraying are solved.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] A spray-free polyurethane self-skin foam material, which contains the following components in mass parts:

[0009] The A material contains:

[0010]

[0011] The B material contains diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate and urethane-modified diphenylmethane diisocyanate.

[0012] In the A material of the present application, the polyether polyol with a functionality of 3 has a number average molecular weight of 4000-6000 and a hydroxyl value of 10-50 mgKOH / g, and the polymerization units are propylene oxide and ethylene oxide, and the mass fraction of ethylene oxide is 5%-30% based on the total mass of propylene oxide and ethylene oxide. Suitable examples include but are not limited to F3135 and F3128 of Wanhua Chemical.

[0013] The graft polyether polyol described in the present application has a hydroxyl value of 18-32 mgKOH / g, preferably a hydroxyl value of 20-24 mgKOH / g; wherein the styrene and acrylonitrile solid content is 30-50%, preferably a solid content of 35-45%; the graft polyether polyol content in the A material is greater than 30%, preferably 40-50%, based on the total weight of the A material. Suitable examples include but are not limited to Wanhua Chemical's POP2140, POP3630.

[0014] The alcohol chain extender described in the present application is one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,2-pentanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol monoethyl ether, or neopentyl glycol.

[0015] The catalyst described in the present application does not contain a strong catalyst for initiating, specifically bis(dimethylaminoethyl) ether (A1), triethylenediamine (A33), pentamethyldiethylene triamine, trimethylhydroxyethyl ethylenediamine, N,N,N'-trimethyl-N'-hydroxyethyl bisaminoethyl ether (ZF10), 2,2-bis morpholino diethyl ether, and does not add any one or more.

[0016] The catalyst described in the present application includes one or more of (1) organometallic catalysts and (2) gel and / or balanced amine catalysts.

[0017] Preferably, the organometallic catalysts include one or more of dibutyltin dilaurate, dioctyltin dilaurate, stannous octoate, dibutyltin diacetate, dibutyltin mercaptide, dioctyltin mercaptide, dioctyltin dithioacetate, dimethyltin dithioacetate, zinc carboxylate, bismuth carboxylate.

[0018] Preferably, the gel and / or balanced amine catalysts include at least one of dimethylcyclohexylamine, N-methyl dicyclohexylamine, pentamethyl diisopropylamine, dimethyl ethanolamine, dimethylaminoethoxy ethanol, trimethylhydroxyethylpropylenediamine, N,N-bis(dimethylaminopropyl) isopropanolamine, bis(dimethylamino)-2-propanol, dimethylaminopropylamine diisopropanol, N-ethyl morpholine, 1,2-dimethylimidazole, diazabicyclo, 1,4-dimethylpiperazine, tris(dimethylaminopropyl)amine, triethylamine, tetramethyliminodipropylamine.

[0019] The anti-aging aids in the A material described in the present application include one or more of light stabilizers and antioxidants.

[0020] Preferably, the light stabilizer comprises a hindered amine light stabilizer, suitable examples include but are not limited to one or more of poly(succinato-4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethyl) ester, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate.

[0021] Preferably, the light stabilizer can also comprise one or more benzotriazole-based ultraviolet absorbers, suitable examples include but are not limited to one or more of ethyl 4-[[(methylphenylamino)methyl]amino]benzoate, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-4,6-bis(tert-amyl)phenol, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3-dodecyl-5-methyl)-benzotriazole, 2,4-bis(2',4'-dimethylphenyl)-6-(2'-hydroxy-4'-octyloxy)-1,3,5-triazine.

[0022] Preferably, the antioxidant includes but is not limited to one or more of triethylene glycol bis-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 2,6-di-tert-butyl-4-methylphenol, pentaerythrityl tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3,5-di-tert-butyl-4-hydroxyphenyl propionate octadecyl ester, N,N-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hexylenediamine, isooctyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate.

[0023] Preferably, among the diphenylmethane diisocyanates, the content of 4,4'-diphenylmethane diisocyanate is more than 99%, at room temperature it is a white to light yellow-green crystal solid, and after melting it is a transparent liquid, such as WANNATE MDI-100 of Wanhua Chemical.

[0024] The polymeric diphenylmethane diisocyanate is a polymeric MDI, which is a mixture of polymethylene polyphenyl diisocyanates with different functionalities, such as WANNATE PM200 of Wanhua Chemical.

[0025] The urethane-modified diphenylmethane diisocyanate is generally produced by reacting polyether polyols or polyester polyols with MDI to generate urethane-modified MDI with -NCO terminal groups, such as Wanhua Chemical's WANNATE8617, WANNATE 8618, and WANNATE 8605.

[0026] The content of urethane-modified diphenylmethane diisocyanate in component B is 40-60%, the content of diphenylmethane diisocyanate is 20-40%, and the content of polymeric diphenylmethane diisocyanate is 15-30%, based on the total weight of component B.

[0027] The isocyanate group (NCO) mass fraction of material B in this invention is 20-30%, preferably 24-28%.

[0028] In this invention, material B, with appropriate diphenylmethane diisocyanate, can provide good open-cell effect for foam, reduce or avoid the occurrence of pinholes, and meet appearance requirements. At the same time, urethane-modified diphenylmethane diisocyanate ensures the required toughness of foam, while polymerized diphenylmethane diisocyanate provides sufficient crosslinking degree to ensure wear resistance.

[0029] The color paste described in this invention is a black or other desired color paste suitable for commercially available polyurethane.

[0030] The physical foaming agent of the present invention is one or more of hydrochlorofluorocarbons, hydrofluorocarbons, and alkanes, preferably one or more of 1,1-dichloro-1-fluoroethane, cyclopentane, pentane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, 1,1,1,2-tetrafluoroethane, and 1-chloro,3,3,3-trifluoropropene.

[0031] The low surface energy particles described in this invention are particles with a surface energy of less than 25 mN / m, a size of 1-500 micrometers, and uniform dispersion, preferably polytetrafluoroethylene particles. After adding these low surface energy particles, the particles are uniformly distributed on the foam surface, reducing the overall surface energy of the foam, improving the smoothness of the surface to the touch, and significantly enhancing wear resistance.

[0032] A method for preparing a paint-free, self-skinning foam product includes the following steps: A closed-mold casting process is used. After spraying a release agent onto the mold, materials A and B are mixed evenly using a high-pressure foaming machine at a mass ratio of A:B = 100:30-60, preferably 100:40-50. The mixture is then poured into the mold and cured for 90-120 seconds before the mold is opened to obtain the paint-free product. The material temperature is maintained at 20-30℃, and the mold temperature is maintained at 50℃-60℃.

[0033] Compared with existing technologies, this invention has the following beneficial effects: This invention provides a high-performance polyurethane self-skinning foam material that does not require in-mold coating. This is achieved by increasing the amount of grafted polyether, adding low surface energy particles, avoiding the use of strong foaming catalysts, and adjusting the A component with the addition of anti-aging additives. A physical foaming agent is used for foaming. The appearance is consistent with painted foam, with no color difference, no pinholes, and gloss and feel are essentially the same as painted foam. Yellowing resistance and abrasion resistance meet requirements, and other common self-skinning foam performance requirements are also met. This solves the environmental pollution, increased costs, and employee health problems caused by the need for in-mold coating of existing polyurethane self-skinning foam materials, reduces production steps, and further improves production efficiency. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0035] Unless otherwise specified in the embodiments and comparative examples of this invention, the conditions were performed under conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, were commercially available products.

[0036] The raw materials used in the examples and comparative examples are shown below:

[0037] Material A components:

[0038] Polyether polyol 1, functionality 3, glycerol-initiated, hydroxyl value 35 mg KOH / g, polymerized from propylene oxide and ethylene oxide, ethylene oxide content 15%, based on the total mass of propylene oxide and ethylene oxide;

[0039] Polyether polyol 2, functionality 3, glycerol-initiated, hydroxyl value 28 mg KOH / g, polymerized from propylene oxide and ethylene oxide, ethylene oxide content 15%, based on the total mass of propylene oxide and ethylene oxide;

[0040] Grafted polyether polyol 1, functionality 3, glycerol-initiated, hydroxyl value 26 mg KOH / g, polymerized from propylene oxide and ethylene oxide, viscosity 5000-5800 mpa·s, solid content of acrylonitrile and styrene 40%;

[0041] Grafted polyether polyol 2, functionality 3, glycerol-initiated, hydroxyl value 24 mg KOH / g, polymerized from propylene oxide and ethylene oxide, viscosity 2900-3200 mpa·s, solid content of acrylonitrile and styrene 30%;

[0042] Alcohol chain extenders: ethylene glycol;

[0043] Catalysts: Triethylenediamine, Dimethylaminopropylamine diisopropanol, Dioctyltin mercaptan, Dibutyltin mercaptan;

[0044] Anti-aging additives: 2-(2'-hydroxy-3-dodecyl-5-methyl)benzotriazole, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, isooctyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate;

[0045] Physical foaming agents: dichlorofluoroethane, 1-chloro,3,3,3-trifluoropropylene;

[0046] Low surface energy particles: polytetrafluoroethylene particles, average diameter 200μm, DAIKIN, Japan;

[0047] Pigment: Black pigment;

[0048] Component B:

[0049] Diphenylmethane diisocyanate: WANNATE MDI-100F, NCO content 33.6wt%, Wanhua Chemical;

[0050] Polymeric diphenylmethane diisocyanate: WANNATE PM200, NCO content 31.0wt%, Wanhua Chemical;

[0051] Carbamate-modified isocyanate: WANNATE 8617, NCO content 23wt%, Wanhua Chemical.

[0052] The paint-free polyurethane material was prepared according to the components shown in Table 1 in Examples 1-4 and Comparative Examples 1-5.

[0053] Table 1 Raw Materials and Usage

[0054]

[0055] Example 1

[0056] Preparation of component A: The measured materials of component A shown in Table 1 are added into the reactor and stirred at room temperature for 1 hour, and then discharged to obtain component A;

[0057] Preparation of Material B:

[0058] The measured material of component B shown in Table 1 is added into the reactor and stirred at room temperature for 1 hour before being discharged to obtain component B.

[0059] Preparation of self-skinning foam products that do not require spraying:

[0060] A closed-mold injection process is adopted. After the mold is sprayed with a release agent, materials A and B are mixed evenly according to the mass ratio in Table 1 using a high-pressure foaming machine and then injected into the mold. After curing for 90 seconds, the mold is opened to obtain a self-skinning foam product that does not require spraying. The material temperature is maintained at 30℃ and the mold temperature is maintained at 60℃.

[0061] Example 2

[0062] The material temperature is maintained at 25°C, and the mold temperature is maintained at 55°C. The rest is the same as in Example 1.

[0063] Example 3

[0064] The material temperature is maintained at 25°C, and the mold temperature is maintained at 50°C. The rest is the same as in Example 1.

[0065] Example 4

[0066] The material temperature is maintained at 25°C, and the mold temperature is maintained at 55°C. The rest is the same as in Example 1.

[0067] Comparative Example 1

[0068] The material temperature is maintained at 30°C, and the mold temperature is maintained at 60°C. The rest is the same as in Example 1.

[0069] Comparative Example 2

[0070] The material temperature is maintained at 25°C, and the mold temperature is maintained at 55°C. The rest is the same as in Example 1.

[0071] Comparative Example 3

[0072] The material temperature is maintained at 25°C, and the mold temperature is maintained at 55°C. The rest is the same as in Example 1.

[0073] Comparative Example 4

[0074] The material temperature is maintained at 30°C, and the mold temperature is maintained at 60°C. The rest is the same as in Example 1.

[0075] Comparative Example 5

[0076] The material temperature is maintained at 30°C, and the mold temperature is maintained at 60°C. The rest is the same as in Example 1.

[0077] Performance testing: The paint-free products described in Examples 1-4 and Comparative Examples 1-4, including paint-free articles, were subjected to the following tests:

[0078] Appearance

[0079] Density ISO 845

[0080] Hardness (Shore A) ISO 868

[0081] Light aging resistance of HONDA DWG NO 7850Z: aging time 400 hours, backplate temperature 83℃

[0082] Abrasion-resistant HONDA DWG NO 7850Z: Load 1.3Kg, contact with double-sided 100mm*45mm cotton cloth, speed 50 times / min, dry friction 6000 times followed by wet friction with artificial sweat to complete one cycle test.

[0083] Odor PV3900

[0084] VOC VDA275

[0085] The test results are summarized in Table 2.

[0086] Table 2 Test Results

[0087]

[0088]

[0089] ND* means not detected.

[0090] The test results of the comparative examples and comparative examples show that the high-performance paint-free material of the present invention still has a good appearance, no pinholes and color difference, meets the requirements of wear resistance and yellowing, and meets the requirements of other conventional foam products. At the same time, it can be demolded quickly within 90 seconds.

[0091] A comparison of Example 1 and Comparative Example 1 reveals that polyurethane materials without the selected grafted polyether polyol content of the present invention cannot simultaneously meet the requirements of no pinholes and color difference. A comparison of Example 2 and Comparative Example 2 reveals that polyurethane materials without the selected polytetrafluoroethylene particles of the present invention cannot simultaneously meet the requirements of abrasion resistance. When the pigment content is lower than the range described in the present invention (Example 3 and Comparative Example 3), the color difference distribution is significantly different, and surface color difference can be observed with the naked eye, and the light resistance performance is unqualified. A comparison of Example 4 and Comparative Example 4 reveals that polyurethane materials without the selected anti-aging additive of the present invention cannot meet the requirements of yellowing and light resistance. A comparison of Example 1 and Comparative Example 5 reveals that the use of a strong aeration catalyst leads to a significant decrease in abrasion resistance, which may cause the foam to fail to meet the abrasion resistance requirements.

[0092] In summary, the preparation method of this invention, through the extensive use of grafted polyether, supplemented with anti-aging agents, color pastes, low surface energy particles, etc., and adjusted according to the B component, produces a polyurethane material that fully meets the conventional performance requirements and production process of self-skinning foam without the need for in-mold coating. It possesses a good appearance and excellent wear resistance and light resistance. This solves the problems of environmental pollution, reduced production efficiency, and high scrap rate caused by in-mold coating during the production of self-skinning foam.

Claims

1. A spray-free, self-skinning polyurethane foam material, comprising the following components, in parts by weight: Material A includes: 20-40 polyether polyols with a functionality of 3; 30-60% grafted polyether polyol; Alcohol chain extenders 5-10; Catalyst 0.5~3; Anti-aging additives 1-4; Pigment 2~8; Physical foaming agent 5~10; Water 0.1~1; Low surface energy particles 0.1~1; Material B comprises diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, and urethane-modified diphenylmethane diisocyanate; the content of urethane-modified diphenylmethane diisocyanate in Material B is 40-60%, the content of diphenylmethane diisocyanate is 20-40%, and the content of polymeric diphenylmethane diisocyanate is 15-30%, based on the total weight of Material B; The catalyst does not contain a strong initiation catalyst, which includes bis(dimethylaminoethyl) ether, triethylenediamine, pentamethyldiethylenetriamine, trimethylhydroxyethylethylenediamine, N,N,N'-trimethyl-N'-hydroxyethyl bisaminoethyl ether, and 2,2-bismorpholinodiethyl ether.

2. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, Material A contains the following components, in parts by mass: Polyether polyols with a functionality of 3, 25-35; 40-50% grafted polyether polyol; Alcohol chain extenders 6-8; Catalyst 1~2; Anti-aging additives 1-2; Colorant 3~6; Physical foaming agent 6~8; Water 0.2~0.3; Low surface energy particles 0.2~0.

3.

3. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The grafted polyether has a hydroxyl value of 18-32 mgKOH / g; the solid content of styrene and acrylonitrile is 30-50%; the content of grafted polyether polyol in material A is greater than 30%, based on the total weight of material A.

4. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The grafted polyether has a hydroxyl value of 20-24 mgKOH / g; the solid content of styrene and acrylonitrile is 35-45%; the content of grafted polyether polyol in component A is 40-50%, based on the total weight of component A.

5. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The polyether polyol has a functionality of 3, a number average molecular weight of 4000-6000, a hydroxyl value of 10-50 mgKOH / g, and its polymerization units are propylene oxide and ethylene oxide, wherein the mass percentage of ethylene oxide is 5%-30% based on the total mass of propylene oxide and ethylene oxide.

6. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The alcohol chain extender is one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,2-pentanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, and neopentanediol.

7. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The physical foaming agent is one or more of hydrochlorofluorocarbons, hydrofluorocarbons, and alkanes.

8. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The physical foaming agent is one or more of 1,1-dichloro-1-fluoroethane, cyclopentane, pentane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, 1,1,1,2-tetrafluoroethane, and 1-chloro,3,3,3-trifluoropropene.

9. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The low surface energy particles are particles with a surface energy of less than 25 mN / m, a size of 1-500 micrometers, and uniform dispersion.

10. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The low surface energy particles are polytetrafluoroethylene particles.

11. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The isocyanate group mass fraction of the B material is 20-30%.

12. The spray-free self-skinning polyurethane foam material according to claim 1, characterized in that, The isocyanate group mass fraction of the B material is 24-28%.

13. A method for preparing the paint-free self-skinning polyurethane foam material according to any one of claims 1-12, comprising the following steps: using a closed-mold casting process, after spraying a release agent onto the mold, mixing materials A and B uniformly at a mass ratio of A:B=100:30-60 using a high-pressure foaming machine, pouring the mixture into the mold, curing for 90-120 seconds, and then opening the mold to obtain the paint-free self-skinning foam product, wherein... The material temperature is maintained at 20-30℃, and the mold temperature is maintained at 50℃-60℃.

14. The method according to claim 13, characterized in that, The mass ratio of materials A and B is A:B = 100:40-50.

Images