Polyurethane skin material and preparation method thereof

Abstract

The invention discloses a polyurethane skin material and a preparation method thereof, the skin material comprises the following components: (A) an isocyanate component and (B) an isocyanate reactive component, and the surface tension of the isocyanate reactive component is 20-35 mN / m. The skin material disclosed by the invention is not easy to generate bubbles, and the prepared decorative skin has good appearance and can be applied to various fields such as automobile interior and exterior decorations, composite materials, seat imitation leather and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane, and in particular relates to a polyurethane surface material capable of overcoming surface defects caused by process bubbles and a preparation method thereof. Background Art

[0002] Traditional genuine leather products are widely used in shoes, home furnishings, automotive interior and exterior decoration, clothing and other fields due to their unique texture and aesthetics. However, their high prices, monotonous styles and complicated maintenance procedures have greatly limited their application scope. In comparison, polyurethane surface materials have the advantages of low cost, diverse styles, easy maintenance, and water and stain resistance, making them gradually become the mainstream of the market.

[0003] However, there are still some problems in the actual production process of the existing polyurethane skin materials. First, for the two-component polyurethane system, physical and mechanical bubbles are inevitably mixed into the polyurethane composition during the mixing reaction, or the trace amount of moisture in the polyurethane composition itself causes the gas generated by foaming to gather and float up, which will cause defects such as bubbles and pinholes on the surface of the skin material, seriously affecting the production and application of decorative skin materials.

[0004] There are usually two existing solutions to improve the appearance defects of polyurethane skins. One is to perform physical defoaming by introducing a defoaming agent, and the other is to inhibit the floating of bubbles by accelerating the reaction process of the polyurethane system. However, both have shortcomings. For the former, the effect of the defoaming agent is too long, usually taking several hours, which greatly reduces the production efficiency. For the latter, the reaction process of the polyurethane system is accelerated to speed up the curing of the system, and the process operation period is greatly shortened, which limits the production of large-sized skin products.

[0005] Therefore, how to create a polyurethane skin material and its preparation method that can effectively prevent bubbles and pinhole defects caused by mechanical foaming and floating in the polyurethane system and improve the process tolerance and process stability of industrial production has become the focus of research in the industry. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a polyurethane skin material and a preparation method thereof, which can overcome the surface defects caused by process bubbles, can quickly increase viscosity, have high foam stability, and greatly improve the process tolerance and process stability of the industrial production of polyurethane skins.

[0007] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0008] A polyurethane skin material comprises the following components:

[0009] (A) an isocyanate component,

[0010] (B) an isocyanate-reactive component,

[0011] Wherein, the surface tension of the isocyanate reactive component is 20-35 mN / m;

[0012] Preferably, the isocyanate component is a compound containing an isocyanate terminal group in the molecular structure, including one or more of aromatic isocyanate, alicyclic isocyanate and aliphatic isocyanate. Aromatic isocyanate can provide higher strength and toughness, and the raw materials are easily available, low-priced, and widely used in industry, but such aromatic isocyanate usually has the disadvantage of yellowing after long-term light exposure; while alicyclic isocyanate and aliphatic isocyanate are non-yellowing isocyanates, which are suitable for environments with higher yellowing resistance requirements for the decorative skin, and those skilled in the art can choose according to their needs.

[0013] Preferably, the isocyanate component includes but is not limited to toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylylene diisocyanate, cyclohexane dimethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, tetramethyl meta-xylylene diisocyanate, norbornane diisocyanate, dimethyl biphenyl diisocyanate, methylcyclohexyl diisocyanate, tetramethylene diisocyanate, 2-methylpentamethylene diisocyanate, dodecamethylene diisocyanate. Cyanate, 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-2,2-dicyclohexylpropane, poly(hexamethylene diisocyanate), octamethylene diisocyanate, toluene-α,4-diisocyanate, 2,4,6-trimethyl-1,3-phenylene diisocyanate, 4-chloro-6-methyl-1,3-phenylene diisocyanate, 1,4-butane diisocyanate, 1,8-octane diisocyanate, and the like, as well as modified isocyanates, prepolymers, dimers, polymers (including trimers or higher) and other isocyanate derivatives of the above isocyanates. Such isocyanate compounds can be used alone or in combination.

[0014] In a preferred embodiment, the component A is preferably a polyether-modified isocyanate. Preferably, the polyether-modified isocyanate has an NCO content of 15 to 31 wt % and a viscosity of 50 to 1000 mPa·s (25° C.).

[0015] The isocyanate reactive component comprises the following components in mass fractions:

[0016] Polyol component 70wt.%-90wt.%,

[0017] Chain extender 5wt.%-20wt.%,

[0018] Catalyst 0.01-1wt.%

[0019] Thickener 0.2~2wt.%

[0020] Surfactant 0.2-4wt.%

[0021] Other additives 0-10wt.%.

[0022] Preferably, the polyol component includes polyether polyol and polyester polyol. In the present invention, the polyester polyol includes polyether carbonate polyol and polycarbonate polyol.

[0023] Preferably, the polyol component is a polyether polyol, such as a polyether polyol with a functionality of 2, and the preferred initiator can be ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, neopentyl glycol, etc.; the preferred initiator for the polyether polyol with a functionality of 3 can be glycerol, trimethylolpropane, etc. The polyether polyol is preferably prepared by ring-opening homopolymerization or copolymerization using propylene oxide, ethylene oxide or a combination of the two as polymerization monomers.

[0024] In order to obtain the appropriate surface tension range of the isocyanate reactive component required by the present invention, the addition of the polyol component can be adjusted by mixing a plurality of polyol components to achieve an appropriate surface tension.

[0025] In a preferred embodiment, the polyol component includes polyether polyol 1, with an average functionality of 2-3 and a number average molecular weight of 1000-8000 g / mol, and its amount is 70 wt.%-90 wt.% of the total mass of the isocyanate reactive component.

[0026] In a preferred embodiment, the isocyanate reactive component further comprises polyether polyol 2, with an average functionality of 2-3 and a number average molecular weight of 200-500 g / mol, and its amount is 0wt.%-20wt.% of the total mass of the isocyanate reactive component.

[0027] Preferably, the chain extender is a small molecule polyol with an average functionality of 2-3 and a molecular weight of 60-180 g / mol. Preferred examples include, but are not limited to, ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-pentanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, neopentyl glycol, glycerol, trimethylolpropane, etc. Such small molecule polyols can be used alone or in combination.

[0028] The catalyst comprises an organic metal catalyst or / and an amine catalyst, preferably selected from one or more of triethylamine, tributylamine, triethylenediamine, N-ethylmorpholine, N,N,N',N'-tetramethyl-ethylenediamine, pentamethyldiethylene-triamine, N,N-methylaniline, N,N-dimethylaniline, tin (II) acetate, tin (II) octoate, tin ethylhexanoate, tin laurate, dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, dibutyltin maleate, dioctyltin diacetate, zinc isooctanoate, dibutyltin diacetate, dibutyltin maleate and dioctyltin diacetate, bismuth neodecanoate, bismuth 2-ethylhexanoate, and bismuth octoate.

[0029] The thickener is a physical thickener or a chemical thickener. Preferred examples of the physical thickener include, but are not limited to, one or more of fumed silica, bentonite, and hydrogenated castor oil, which functions to generate intermolecular forces such as hydrogen bonds in the polyurethane system to form a three-dimensional network structure, thereby increasing the viscosity of the system by several to dozens of times. When an external force is applied to the system, the three-dimensional network structure is destroyed, so that the polyurethane system generates fluidity to meet the requirements of process production.

[0030] The chemical thickener is selected from an active chain extender having at least one free primary -NH2 group that can react with isocyanate, preferably an aromatic diamine. Preferred examples of the chemical thickener include, but are not limited to, one or more of diethyltoluenediamine, 4,4'-methylenebis(2-ethyl-6-methylaniline), 4,4'-methylenebis(2,6-diethylaniline), and diethyltoluenediamine is particularly preferred. The chemical thickener functions to rapidly react with the isocyanate component to extend the chain, thereby rapidly increasing the viscosity of the polyurethane system.

[0031] It should be noted that at 25°C, the viscosity of the isocyanate reactive component and the isocyanate component tested 10 seconds after mechanical mixing can reach 2000-8000 mPa·s. This viscosity range can inhibit the movement of bubbles in the polyurethane composition while taking into account the fluidity of the raw materials, which is mainly achieved through the action of the thickener.

[0032] In particular, adjusting the amount of catalyst, such as increasing the amount of catalyst, can help adjust the viscosity of the isocyanate reactive component and the isocyanate component after mixing. In order to avoid the polyurethane composition from gelling and curing quickly and thus losing fluidity. Therefore, it is necessary to control the amount of catalyst used so that at 25°C, the gel time of the isocyanate component and the isocyanate reactive component after being fully mechanically mixed should be 15-60s.

[0033] The surfactant comprises a non-silicone surfactant and a silicone surfactant, preferably a silicone surfactant, and particularly preferably a polyether-modified silicone surfactant. The surfactant can be obtained through commercial purchase or can also be prepared by a conventionally known method. Preferably, the surfactant is used in an amount of 0.2-4wt.%, more preferably 0.4-2wt.%, based on the total weight of the isocyanate-reactive component.

[0034] The addition of surfactants can effectively adjust the surface tension of the isocyanate reactive components, and the surface tension of the isocyanate reactive components can be further adjusted within the scope of the present invention by adjusting the type and amount of surfactant added to help prevent mechanical foaming in the polyurethane composition.

[0035] The other additives are selected from one or more of internal release agents, flame retardants, fillers, pigments, antioxidants, light stabilizers, auxiliary antioxidants, hydrolysis stabilizers, bactericides and mildewicides, leveling agents, wetting agents, reactive diluents, coupling agents, color pastes, and water removers. Preferably, the amount of the additives is 4-10wt% of the total weight of the isocyanate reactive components.

[0036] The surface tension of the isocyanate reactive component in the present invention is the result of mixing multiple components, and can be achieved in various ways such as adjusting the content and type of the added components.

[0037] In order to achieve a decorative effect on the appearance of the polyurethane skin material, the thickness of the skin prepared by the polyurethane skin material should be 0.5-3 mm.

[0038] Preferably, the equivalent ratio of isocyanate groups to hydroxyl groups in the isocyanate component and the isocyanate-reactive component is 0.95-1.15, preferably 0.98-1.08.

[0039] The present invention also provides a method for preparing the polyurethane skin material: mixing the isocyanate component and the isocyanate reactive component to react to obtain the polyurethane skin material;

[0040] Preferably, the isocyanate component and the isocyanate reactive component are mixed by a high-pressure foaming machine, the mixing pressure of the high-pressure foaming machine is preferably 100-140 bar, and the injection rate is preferably 150-350 g / s. The mixing pressure and injection rate of the present invention are conducive to the complete reaction of the isocyanate component and the isocyanate reactive component, which is conducive to thorough curing and maintaining the performance of the surface material.

[0041] The mold temperature is preferably 50-100° C., the material temperature is 25-40° C., and the reaction time is preferably 1-5 min.

[0042] The beneficial effects of the present invention are:

[0043] The invention provides a polyurethane system with rapid viscosity increase and high foam stability. By controlling the surface tension of the isocyanate reactive component and the initial viscosity of the polyurethane reaction mixture, the two can cooperate to evenly and stably disperse the gas originally existing in the system or the mechanical bubbles introduced by the process, without breaking and agglomerating to form large cavitations or floating to form surface defects, thereby greatly improving the process tolerance and process stability of the industrial production of polyurethane surface materials. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0046] Main raw material sources

[0047] The raw materials used in the specific embodiment are as follows:

[0048] Isocyanate 1-1, WANNATE 8629, NCO 26wt%, Wanhua Chemical;

[0049] Isocyanate 1-2, WANNATE 8617, NCO 23wt%, Wanhua Chemical;

[0050] Polyether polyol 2-1, functionality three, initiated by propylene glycol, polymerized by propylene oxide and ethylene oxide, ethylene oxide content 90%, number average molecular weight 1000, Wanhua Chemical;

[0051] Polyether polyol 2-2, functionality is di, initiated by propylene glycol, ring-opening polymerization of propylene oxide, terminated by ethylene oxide, number average molecular weight 8000, Wanhua Chemical;

[0052] Polyether polyol 2-3, functionality three, initiated by propylene glycol, polymerized by propylene oxide and ethylene oxide, ethylene oxide content 65%, number average molecular weight 4000, Wanhua Chemical;

[0053] Polyether polyol 2-4, functionality is di, propylene oxide polymerization, ethylene oxide end-capping, number average molecular weight 3000, Wanhua Chemical;

[0054] Polyester polyol 2-5, functionality is two, obtained by polycondensation of adipic acid and ethylene glycol, number average molecular weight 2000, Yantai Huada Chemical;

[0055] Polyester polyol 2-6, functionality is two, obtained by polycondensation of adipic acid and 1,4-butanediol, number average molecular weight 4000, Yantai Huada Chemical;

[0056] Polyether polyol 2-7, functionality is three, initiated by glycerol, polymerized by propylene oxide and ethylene oxide, ethylene oxide content 60%, number average molecular weight 280, Jiahua Chemical;

[0057] Polyether polyol 2-8, functionality three, propylene glycol initiated, propylene oxide polymerized, number average molecular weight 400, Bluestar Dongda Chemical;

[0058] Polyester polyol 2-9, functionality is two, obtained by polycondensation of adipic acid and ethylene glycol, number average molecular weight 450, commercially available, Yantai Huada Chemical;

[0059] Small molecule polyol 3-1, ethylene glycol, Henan Wanhai Chemical;

[0060] Small molecule polyol 3-2,1,4-butanediol, Wanhua Chemical;

[0061] Small molecule polyol 3-3, propylene glycol, Yijia Chemical;

[0062] Thickener 1, diethyltoluenediamine, Yarui Chemical;

[0063] Thickener 2, fumed silica, DeLan Chemical;

[0064] Surfactant 1, B8002, Evonik;

[0065] Surfactant 2, B8409, Evonik;

[0066] Catalyst, Fomrez UL-29, Momentive;

[0067] Black paste, added holy new materials.

[0068] Main test methods

[0069] Surface tension test standard: GB / T 22237-2008.

[0070] Viscosity test: GB / T 12008.7-2010.

[0071] Gel test: Start timing from the moment the raw material is ejected from the gun head of the high-pressure foaming machine. Lightly touch the surface of the raw material with the end of a plastic dropper until the surface of the raw material is no longer sticky to the dropper. This time is marked as the gel time of the raw material.

[0072] Appearance judgment: The appearance of the polyurethane skin product is judged by observing its outer surface.

[0073] Example

[0074] The ingredients and amounts of the embodiments are listed in Table 1, in parts by weight.

[0075] Table 1 Example formulation (parts by weight)

[0076]

[0077]

[0078] Comparative Example

[0079] The components and dosage of the comparative example are listed in Table 2, in parts by weight.

[0080] Table 2 Comparative Example Formula (parts by weight)

[0081]

[0082]

[0083] After fully mixing the units of component B listed in Table 1 and Table 2, an isocyanate reactive component is obtained, and the weight ratio of the isocyanate reactive component and the isocyanate reactive component is calculated according to a hydroxyl equivalent ratio of 1.03, and the components are mixed by a high-pressure spraying system and applied to a metal mold previously coated with a release agent. The mold temperature is set to 70°C, and the mold is opened and sampled after maintaining the pressure for 3 minutes to obtain the polyurethane skin. The appearance of the product is determined by observing its outer surface. The appearance results of the polyurethane skin products of the embodiment and the comparative example are listed in Table 3 and Table 4, respectively.

[0084] Table 3 Appearance results of the skin products of the examples

[0085]

[0086] Table 4 Appearance results of comparative skin products

[0087] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Skin thickness, mm 0.3 4.5 1.5 1.2 1.3 bubble many none less More none Pinhole many none less none none filling good Difference good good good Is the surface oily? no no no no yes

[0088] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited thereto. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A polyurethane skin material, characterized in that: Includes the following components: (A) an isocyanate component, (B) an isocyanate-reactive component, Wherein, the surface tension of the isocyanate reactive component is 20-35 mN / m.

2. The polyurethane skin material according to claim 1, characterized in that: The isocyanate component comprises one or more of aromatic isocyanate, alicyclic isocyanate and aliphatic isocyanate, preferably aromatic isocyanate; Preferably, the isocyanate component includes but is not limited to toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylene diisocyanate, cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, tetramethyl metaxylene diisocyanate, norbornane diisocyanate, dimethyl biphenyl diisocyanate, methylcyclohexyl diisocyanate, tetramethylene diisocyanate, 2-methylpentamethylene diisocyanate. diisocyanate, dodecamethylene diisocyanate, 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-2,2-dicyclohexylpropane, poly(hexamethylene diisocyanate), octamethylene diisocyanate, toluene-α,4-diisocyanate, 2,4,6-trimethyl-1,3-phenylene diisocyanate, 4-chloro-6-methyl-1,3-phenylene diisocyanate, 1,4-butane diisocyanate, 1,8-octane diisocyanate, and one or more of the modified, prepolymer, dimer, and polymer isocyanate derivatives of the above isocyanates; Preferably, the component A is a polyether-modified isocyanate, and more preferably, the polyether-modified isocyanate has an NCO of 15 to 31 wt % and a viscosity of 50 to 1000 mPa·s (25° C.).

3. The polyurethane skin material according to claim 1 or 2, characterized in that: The isocyanate reactive component comprises the following components in mass fractions: Polyol component 70wt.%-90wt.%, Chain extender 5wt.%-20wt.%, Catalyst 0.01-1wt%, Thickener 0.2~2wt% Surfactant 0.2-4wt%, Other additives 0-10wt%.

4. The polyurethane skin material according to any one of claims 1 to 3, characterized in that: The polyol component includes polyether polyol and polyester polyol; Preferably, the polyol component is a polyether polyol, and preferably, the initiator of the polyether polyol is selected from one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, neopentyl glycol, glycerol, and trimethylolpropane; Preferably, the polyol component comprises polyether polyol 1, having an average functionality of 2-3 and a number average molecular weight of 1000-8000 g / mol, and an amount thereof of 70 wt.%-90 wt.% of the total mass of the isocyanate reactive component; Preferably, the isocyanate reactive component further comprises polyether polyol 2 having an average functionality of 2-3 and a number average molecular weight of 200-500 g / mol, and the amount thereof is 0wt.%-20wt.% of the total mass of the isocyanate reactive component.

5. The polyurethane skin material according to any one of claims 1 to 4, characterized in that: The chain extender is a small molecule polyol with an average functionality of 2-3 and a molecular weight of 60-180 g / mol; Preferably, the chain extender is one or more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-pentanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, neopentyl glycol, glycerol, and trimethylolpropane; Preferably, the catalyst comprises an organic metal catalyst or / and an amine catalyst, preferably one or more selected from triethylamine, tributylamine, triethylenediamine, N-ethylmorpholine, N,N,N',N'-tetramethyl-ethylenediamine, pentamethyldiethylene-triamine, N,N-methylaniline, N,N-dimethylaniline, tin (II) acetate, tin (II) octoate, tin ethylhexanoate, tin laurate, dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, dibutyltin maleate, dioctyltin diacetate, zinc isooctanoate, dibutyltin diacetate, dibutyltin maleate and dioctyltin diacetate, bismuth neodecanoate, bismuth 2-ethylhexanoate, bismuth octoate; Preferably, the thickener is a physical thickener or a chemical thickener; Preferably, the physical thickener includes, but is not limited to, one or more of fumed silica, bentonite, and hydrogenated castor oil; Preferably, the chemical thickener is selected from reactive chain extenders having at least one free primary amino group, preferably aromatic diamines; Preferably, the chemical thickener includes, but is not limited to, one or more of diethyltoluenediamine, 4,4'-methylenebis(2-ethyl-6-methylaniline), and 4,4'-methylenebis(2,6-diethylaniline), and diethyltoluenediamine is particularly preferred.

6. The polyurethane skin material according to any one of claims 1 to 5, characterized in that: At 25°C, the viscosity of the isocyanate reactive component and the isocyanate component measured 10 seconds after mechanical mixing can reach 2000-8000 mPa·s; and / or, At 25°C, the gel time of the isocyanate component and the isocyanate reactive component after sufficient mechanical mixing should be 15-60s.

7. The polyurethane skin material according to any one of claims 1 to 6, characterized in that: The surfactant comprises a non-silicone surfactant and a silicone surfactant, preferably a silicone surfactant, and particularly preferably a polyether-modified silicone surfactant; Preferably, the surfactant is used in an amount of 0.4-2 wt % of the total weight of the isocyanate reactive component; Preferably, the other additives are selected from one or more of internal release agents, flame retardants, fillers, pigments, antioxidants, light stabilizers, auxiliary antioxidants, hydrolysis stabilizers, bactericides and mildewicides, leveling agents, wetting agents, reactive diluents, coupling agents, color pastes, and water removers. Preferably, the amount of the additives is 4-10wt% of the total weight of the isocyanate reactive components.

8. The polyurethane skin material according to any one of claims 1 to 7, characterized in that: The thickness of the skin prepared by the polyurethane skin material is 0.5-3 mm; Preferably, the equivalent ratio of isocyanate groups to hydroxyl groups in the isocyanate component and the isocyanate-reactive component is 0.95-1.15, preferably 0.98-1.

08.

9. The method for preparing the polyurethane skin material according to any one of claims 1 to 8, characterized in that: The isocyanate component and the isocyanate reactive component are mixed and reacted to obtain the polyurethane skin material; Preferably, the isocyanate component and the isocyanate reactive component are mixed by a high-pressure foaming machine, the mixing pressure of the high-pressure foaming machine is preferably 100-140 bar, and the injection rate is preferably 150-350 g / s; Preferably, the mold temperature is 50-100° C., the material temperature is 25-40° C., and the reaction time is 1-5 min.

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