CN112011027A - Preparation method of polyurethane composite material - Google Patents

Abstract

The invention discloses a preparation method of a polyurethane composite material. The preparation method controls the injection pressure of the reactant and the vacuum degree of the mold, and the defined reactant has suitable operation time and lower viscosity. The composite material has the characteristics of low viscosity in the early stage, slow viscosity increase, extremely fast curing speed in the later stage, short demoulding time, etc. The composite material prepared by the method has excellent heat resistance and mechanical properties.

Description

A kind of preparation method of polyurethane composite material

technical field

The invention relates to a preparation method of a polyurethane composite material, in particular to a preparation method of a polyurethane composite material by using a high-pressure injection molding process.

Background technique

High pressure resin transfer molding (HP-RTM) process technology is a new type of process for mass production of high-performance composite materials introduced in recent years. It uses preforms, steel films, vacuum-assisted exhaust, and high-pressure injection , so that the resin liquid can quickly fill the mold cavity and solidify. This process produces products with high efficiency, good dimensional stability, high quality, and low cost of mass production of composite materials, and realizes diversified and complex structural products.

At present, the resins commonly used in the HP-RTM process on the market are mainly epoxy resins and polyurethane resins, but they have the following three shortcomings: (1) the impregnation of the fibers by the resin is not ideal, and the product porosity is high; (2) the resin can be operated The matching of time and molding speed is not good, and it is difficult to achieve high quality and high production speed coordination; (3) In the mold cavity with large area and complex structure, it is impossible to predict and control, and the resin flow is unbalanced.

Patent CN106232671A discloses a composite fiber part and its manufacture, the technical solution is a fiber composite part obtained by impregnating fibers with a polyurethane reactive resin mixture formed of polyisocyanates, polyols, two or more thermally latent catalysts, etc. The molding speed is still relatively slow, the glass transition temperature is only 110 °C, and the heat resistance is not high enough; secondly, the flame retardant performance is not high enough under the condition of adding flame retardants. The above performance still can not meet the demand.

Therefore, it is necessary to provide a technical solution to solve the problems existing in the prior art.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the prior art, the present invention provides a method for preparing a polyurethane composite material. The reactant used in the preparation method has suitable operating time and relatively low viscosity, and has the characteristics of low viscosity in the early stage, slow viscosity growth, extremely fast curing speed in the later stage, and short demoulding time in a high-temperature mold. The prepared composite material has excellent heat resistance and mechanical properties.

A method for preparing a polyurethane composite material, comprising: mixing an isocyanate component and an isocyanate-reactive component, injecting it into a mold with a built-in reinforcing material under a pressure of 80 to 200 bar, preferably 100 to 160 bar for reaction, and the vacuum degree of the mold during the injection process. It is controlled at -0.08～-0.1MPa, preferably -0.085～-0.095MPa, and the composite material is obtained after the reaction; wherein, the isocyanate component comprises polymethylene polyphenyl isocyanate, and the isocyanate reactive component comprises polyether Polyols, catalysts.

The method of controlling the pressure of reactant injection into the mold is well known in the art, such as adjusting the injection pressure through the pressure valve on the HP-RTM equipment; the method of controlling the vacuum degree of the mold is well known in the art, such as by adjusting the mold gap or by vacuum system to adjust etc.

Controlling the injection pressure of the reactant and the vacuum degree of the mold within the scope of the present invention can promote the rapid injection of the reactant into the mold, increase the wettability between the reactant and the built-in reinforcing material in the mold, improve the production efficiency, and reduce the amount of waste in the product. Defects such as poor glue or wrapping bubbles appear.

In a preferred example, after the isocyanate component and the isocyanate-reactive component are mixed, the viscosity within 30 seconds at 50° C. is 30-300 mp.s, preferably 50-200 mp.s. Controlling the viscosity of the reaction mixture can promote the rapid infiltration of the reinforcement material in the mold by the reactant and reduce defects in the product.

The polymethylene polyphenyl isocyanate refers to a mixture of isocyanate compounds with different functionalities that are common in the art, and the obtaining approach can be prepared by a method commonly used in the art, or obtained through commercial procurement. Examples of commercial products include but Not limited to PM-100, PM-130, PM-200, PM-300, PM-400, PM-2010, etc. produced by Wanhua Chemical.

The isocyanate component also optionally includes organic isocyanate monomers, isocyanate prepolymers, other isocyanate modified products, etc., examples of which include but are not limited to toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), Isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), 1,4-ring Hexane diisocyanate (CHDI), xylylene diisocyanate (XDI), cyclohexane dimethylene diisocyanate (HXDI), trimethyl-1,6-hexamethylene diisocyanate (TMHDI), Tetramethyl m-xylylene diisocyanate (TMXDI), norbornane diisocyanate (NBDI), dimethyl biphenyl diisocyanate (TODI), methylcyclohexyl diisocyanate (HTDI), etc. Prepolymers, modified products, etc. Preferably, the NCO content of the isocyanate component is 27.5-33.5%, preferably 30-32%, and the viscosity at 25°C is 5-300 mp.s, preferably 100-250 mp.s.

In a preferred example, the isocyanate component is polymethylene polyphenyl isocyanate and does not contain other types of isocyanate compounds. The isocyanate component only selects polymethylene polyphenyl isocyanate and is used in combination with other components of the present invention. Within the limited scope of the present invention, the effect that can be achieved by using the composite isocyanate component can be achieved, and the The reaction raw material simplifies the process steps and further improves the production efficiency. In particular, compared with the use of isocyanate prepolymer, the reactivity is higher, the curing degree is higher under the same demoulding time, and the dimensional stability of the product is also better, which is more suitable for the production of HP-RTM process that requires rapid curing, At the same time, the mechanical strength and heat resistance of the product will be higher than that of the product using isocyanate prepolymer, which can meet the production of products with higher mechanical performance requirements; in addition, the single raw material composition makes the raw material quality more stable and the product performance better. Stable, it is easier to realize the mass production of products with stable performance and high qualification rate.

The polyether polyol refers to a class of compounds obtained by using polyol as a starter and alkylene oxide as a polymerization monomer. Examples of the starter include but are not limited to ethylene glycol, propylene glycol, 1,4 -Butanediol, 1,3-butanediol, 1,2-butanediol, 1-pentanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, Neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, and the like, examples of such alkylene oxides include, but are not limited to, ethylene oxide, propylene oxide, butylene oxide, and the like.

Preferably, the viscosity of the polyether polyol at 25°C is 30-1000 mp.s, preferably 50-500 mp.s. The viscosity of the polyether polyol needs to be within the range defined by the present invention. When the viscosity is too large, defects such as insufficient fiber infiltration will be caused, especially when preparing large-sized or thick products. The viscosity can get a good product.

Preferably, the polyether polyol has a functionality of 3, is polymerized from propylene oxide, and has a hydroxyl value of 80-800 mgKOH/g, preferably 180-750 mgKOH/g, more preferably 300-600 mgKOH/g.

Polyester polyols, polycarbonate polyols, bio-based polyols, other types of polyether polyols, and the like are also optionally included in the isocyanate-reactive components. In a preferred example, the isocyanate reactive component does not include polyester polyols, polycarbonate polyols, bio-based polyols.

The catalyst refers to a class of compounds that have a catalytic effect on isocyanate groups and active hydrogen atoms, examples of which include, but are not limited to, organometallic catalysts, amine catalysts, and the like.

Preferably, the catalyst comprises at least one heat-sensitive catalyst, and the activation temperature of the heat-sensitive catalyst is not lower than 50°C.

The heat-sensitive catalyst refers to a type of catalyst with obvious catalytic activity at a specific temperature or temperature range, examples of which include but are not limited to blocked amine catalysts, blocked amine catalysts, and highly sterically hindered organic catalysts. Metal catalysts, etc., more specific examples include but are not limited to phenol-terminated 1,8-diazabicyclo[5.4.0]undec-7-ene, formic acid-terminated triethylenediamine, triethylenediamine dicyano Ethyl acetate, dimethyl cyclohexylamine formate or phenate or isooctanoate, dioctyl tin dithiolate, bis(dimethylaminoethyl) ether derivatives, etc., commercial products such as Wan WANALYST KC110, WANALYST KC101, Momentive's UL-32, Air Chemicals' DABCO BL-17, etc. In order to ensure the initial low viscosity of the reaction system, the reaction material is required to be kept at 40 °C or above, and the viscosity increases slowly at the initial stage of injection, and it has a relatively long-term high fluidity. Therefore, the selected catalyst activation temperature should not be lower than 50 °C. , to prevent the catalyst from deblocking and deactivation before the reactant is injected, and also to prevent the rapid increase in the viscosity of the system due to the rapid catalytic reaction in the initial stage of the reactant injection, resulting in product defects such as poor fiber infiltration.

In a preferred example, the catalyst comprises a heat-sensitive catalyst and at least one gel-type catalyst.

The gel-type catalyst is different from the heat-sensitive catalyst, and refers to a type of catalyst that can promote the rapid gelation of the mixed solution. After being added to the reaction system, it can quickly catalyze the reaction between functional groups and improve the gel curing speed of the system. Examples include, but are not limited to, tertiary amine catalysts such as aliphatic amines, alicyclic amines, aromatic amines, and alcohol amines, and metal alkyl compounds such as bismuth, lead, tin, titanium, antimony, mercury, and zinc.

In a preferred example, the catalyst includes only one heat-sensitive catalyst. Only one heat-sensitive catalyst is selected for the catalyst and used in combination with other components of the present invention. Within the limited scope of the present invention, the effect that the composite catalyst system can achieve can be achieved, the reaction raw materials are reduced, and the process steps are simplified , further improving the production efficiency; in addition, the use of a single catalyst can make the reaction system of the system simpler, thereby increasing the stability of the process.

The isocyanate-reactive component also includes a small molecular alcohol with a functionality of 1 to 4, preferably 2 to 3; preferred examples include but are not limited to ethylene glycol, propylene glycol, 1,4-butanediol, 1,3 -Butanediol, 1,2-butanediol, 1-pentanediol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, diethylene glycol, neopentyl glycol, glycerol, triethylene glycol Methylol propane, etc., such small molecular alcohols can be used alone or in combination. The small-molecule alcohol can play the role of chain-extending, cross-linking, and increasing molecular weight of polymer molecules. Further preferably, the small molecular alcohol is selected from one or more of ethylene glycol, propylene glycol, glycerol, and trimethylolpropane.

The isocyanate-reactive component also includes a flame retardant, which can make the resulting composite material have a flame retardant effect. Examples that can be listed include but are not limited to halogenated phosphate ester flame retardants, phosphate ester flame retardants, halogenated Hydrocarbon and other halogen-containing flame retardants, melamine and its salts, reactive flame retardants, inorganic flame retardants, etc. These flame retardants can be used alone or in combination. Preferably, the flame retardant is selected from liquid flame retardants with a viscosity of 40-800 mpa.s at 25°C; further preferably, the flame retardant has a viscosity of 60-400 mpa.s at 25°C; further preferably, the The flame retardant is composed of a reactive flame retardant and a non-reactive flame retardant, and the mass ratio thereof is 1-4:1, preferably 1-3:1. The reactive flame retardant means that the flame retardant itself can participate in the reaction, so that the polyurethane molecule obtained by the reaction has a flame retardant function and has little influence on the material properties. Examples of the reactive flame retardant include but are not limited to three. (Dipropylene glycol) phosphite, N,N-bis(2-hydroxyethyl)aminomethylenephosphonic acid diethyl ester, N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl Methyl ester, commercial products such as WANOLFR-130 and WANOLFR-1830 produced by Wanhua Chemical. The non-reactive flame retardant refers to a type of flame retardant that can play a flame retardant effect but does not participate in the reaction. Examples of the non-reactive flame retardant include but are not limited to tris(2-chloroethyl) ) Phosphate, (2-Chloropropyl) Phosphate, Di(3-bromo-2,2-dimethylpropyl) Phosphate, Dimethyl Methyl Phosphate, Diethyl Ethyl Phosphate, Propyl Phosphate Dimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, etc. The flame retardant is used in combination with other components and processes, within the scope of the present invention, so that the prepared composite material has a good flame retardant effect, and the flame retardant reaches the V0 or V1 level in the UL94 standard. It has a lower viscosity and improves the wettability of the polyurethane composition and reinforcement.

The isocyanate-reactive component also includes an internal mold release agent. The addition of the internal mold release agent can reduce the mold release time of the polyurethane material generated by the reaction and improve the production efficiency. Examples that can be listed include but are not limited to condensation with ester groups. Products, polysiloxane compounds, higher aliphatic alcohols, higher aliphatic amines, zinc stearate, etc., such internal mold release agents can be used alone or in combination.

The isocyanate-reactive component can also optionally be added with dispersants, dyes, antifoaming agents, leveling agents, sizing agents, coupling agents, water scavengers, antioxidants, anti-hydrolysis agents, antistatic agents, depressants. Adhesives, fillers, etc.

In a preferred example, based on the total mass of the isocyanate-reactive components:

The dosage of polyether polyol is 20-89.9%, preferably 45-84%;

The dosage of the catalyst is 0.1-0.7%, preferably 0.2-0.5%;

The dosage of small molecular alcohol is 0-30%, preferably 5-15%;

The amount of the flame retardant is 0-50%, preferably 10-40%.

It should be noted that the preparation method is applicable to a non-foaming system, that is, the reactants are substantially free of water and other physical or chemical foaming agents, and the raw materials used are substantially free of water, or have undergone dehydration treatment, or Add desiccant for drying. In general, the reactant may absorb a small amount of water vapor in the air after contacting with air, or a very small amount of water remains in the raw material. At this time, the water content in the reactant should be controlled below 0.1wt%, preferably below 0.05wt% , it does not affect the implementation of the present invention.

In a preferred example, the molar ratio of isocyanate groups in the isocyanate component to active hydrogen atoms in the isocyanate-reactive component is 0.85-1.25:1, preferably 1-1.2:1.

The reinforcing materials can be selected from commonly used materials in the art, examples of which include but are not limited to glass fibers, carbon fibers, metal fibers, natural fibers, aramid fibers, polyethylene fibers, etc. Such reinforcing materials can be used alone or in combination. Preferably, the reinforcing material is selected from glass fibers and/or carbon fibers.

In a preferred example, based on the total mass of the composite material, the reinforcing material accounts for 10-90%, preferably 30-80%.

In a preferred example, the preparation method adopts a high pressure resin transfer molding process, and the steps include:

At 10-60° C., the isocyanate components are mixed and stirred evenly for use, and the isocyanate-reactive components are mixed and stirred evenly for use;

At 10-60°C, the isocyanate component and the isocyanate-reactive component are mixed uniformly through a static mixer of a high-pressure resin transfer molding equipment, and then injected into a pre-placed reinforcing material with a vacuum degree of -0.08--0.1MPa, Preferably, in a mold of -0.09 to -0.095 MPa, the injection pressure is 80 to 200 bar, preferably 100 to 160 bar, and the mold temperature is controlled to carry out the reaction at 50 to 130° C. After the reaction, a composite material is obtained.

Beneficial effects of the present invention: because each reactant has suitable operation time and low viscosity at the temperature of the processing material, it has the advantages of low viscosity in the early stage, slow growth, extremely fast curing speed in the later stage, and short demoulding time in the high temperature mold , so that the composite material prepared by the resin has better impregnation of the reinforcing material, and at the same time, the product has good dimensional stability, high quality, and excellent mechanical properties, heat resistance and flame retardant properties.

Detailed ways

The raw materials used in the examples and comparative examples are as follows:

Isocyanates:

WANNATE PM200, NCO content 31.2wt%, viscosity 200mpa.s at 25℃, Wanhua Chemical,

WANNATE MDI50, NCO content 33.5wt%, viscosity 10mpa.s at 25℃, Wanhua Chemical,

Isocyanate prepolymer A, NCO content 29.5wt%, viscosity 145mpa.s at 25°C, obtained by reaction of isocyanate compound and polyester polyol, the isocyanate compound is a mixture of WANNATE PM200 and WANNATE MDI50, the polyester polyol The hydroxyl value is 56mgKOH/g, and the functionality is 2;

Polyether polyol 1, starting with glycerin, hydroxyl value 560mgKOH/g, propylene oxide polymerization, viscosity 350mpa.s at 25°C;

Polyether polyol 2, starting with glycerin, hydroxyl value 420mgKOH/g, propylene oxide polymerization, viscosity 380mpa.s at 25°C;

Polyether polyol 3, starting with glycerin, hydroxyl value 336mgKOH/g, propylene oxide polymerization, viscosity 340mpa.s at 25°C;

Polyether polyol starting from 4,1,2 propylene glycol, hydroxyl value is 515mgKOH/g, propylene oxide polymerization, viscosity 70mPas at 25°C;

Heat-sensitive catalyst: WANALYSTKC110 (activation temperature 60℃), Wanhua Chemical;

Heat-sensitive catalyst: BICAT 2536 (activation temperature 72°C), leading chemistry;

Gel catalyst: BICAT8118, leading chemistry;

Reactive flame retardant: WANOL FR-130, Wanhua Chemical, viscosity 500mpa.s at 25℃;

Non-reactive flame retardant: LF11, Jiangsu Jacques Technology Co., Ltd., viscosity 71mpa.s at 25°C;

Internal release agent: HB-650D, TECHNICK PRODUCTS;

Fiberglass cloth: EWR400, China Jushi Co., Ltd.

The test methods or standards adopted in the examples and comparative examples are as follows:

The wettability test method is as follows: the wettability of the composite material is visually observed, and the wettability is “good”, indicating that the inner and outer surfaces of the composite product are smooth, glossy, and free of bubbles, and there is no exposed reinforcing material on the inner and outer surfaces of the resin. Delamination, vacuoles and pores, etc.; the infiltration condition is "bad", which means that the inner and outer surfaces of the composite product are not smooth, or the gloss is poor, or there are air bubbles, or there are partially exposed reinforcing materials on the inner and outer surfaces of the resin, or composite materials. There are obvious phenomena such as delamination, vacuoles and pores;

The viscosity test standard is: GB/T 12008.8-92;

Flexural modulus test standard: DIN ISO 527;

The bending strength test standard is: DIN ISO 527;

The impact strength test standard is: GB/T 1043-2008;

Tensile strength test standard: DIN ISO 527;

The test standard for elongation at break is: DIN ISO 527;

The glass transition temperature test standard is: JY/T 014-1996;

The flame retardant test standard is: GB/T 2408-2008/UL 94.

Resin aging degree test: adopt DSC to test the isocyanate component and the isocyanate reactive component to mix to reach the total amount of exothermic heat (referred to as Q _total ;) of complete curing, take the cured resin sample without any treatment after demoulding and carry out DSC Test to complete curing, record the heat release as Q _sample ; the selected test conditions are kept the same during all the tests, and the curing degree is calculated by the following formula:

The dosage of each component of the polyurethane composition in Examples and Comparative Examples is listed in Table 1.

Table 1

The process conditions for the preparation of the polyurethane composites in the Examples and Comparative Examples are listed in Table 2.

Table 2

According to the raw materials listed in Table 1, the composite materials of Examples and Comparative Examples were prepared by high-pressure resin transfer molding process. :

The isocyanate components are uniformly mixed for subsequent use, respectively, and the isocyanate-reactive components are uniformly mixed for subsequent use;

The isocyanate component and the isocyanate-reactive component are uniformly mixed by a static mixer of a high-pressure resin transfer molding equipment, and then injected into a mold in which the reinforcing material is pre-placed for reaction, and the mold is released after the curing time is reached to obtain a composite material. The resulting composite material does not require post-curing.

The performance test of the composite material prepared by high pressure resin transfer molding process is carried out, and the test results are listed in Table 3.

table 3

What needs to be said is: when the sample is prepared in Comparative Example 2, the injection pressure and vacuum degree are not within the scope of the present invention, resulting in poor wettability of the obtained composite material sample, which is manifested in that there are more exposed glass fibers on the inner and outer surfaces of the composite material product, and the composite material is exposed. There are obvious cavitations and pores in the material plate, which makes it impossible to make a spline that meets the mechanical and other performance testing standards on the entire composite material sample, and it is impossible to perform performance testing.

Claims (10)

1. A method for preparing a polyurethane composite, comprising: mixing an isocyanate component and an isocyanate reactive component, injecting the mixture into a die with a built-in reinforcing material under the pressure of 80-200 bar, preferably 100-160 bar, reacting, controlling the vacuum degree of the die to be-0.08-0.1 MPa, preferably-0.085-0.095 MPa in the injection process, and obtaining the composite material after the reaction is finished; wherein the isocyanate component comprises a polymethylene polyphenyl isocyanate and the isocyanate-reactive component comprises a polyether polyol, a catalyst.

2. A process according to claim 1, characterised in that the viscosity of the isocyanate component and the isocyanate-reactive component after mixing is 30 to 300mp.s, preferably 50 to 200mp.s, at 50 ℃ within 30 seconds.

3. A process according to claim 1 or 2, characterised in that the isocyanate component has an NCO content of 27.5 to 33.5%, preferably 30 to 32%, and a viscosity at 25 ℃ of 5 to 300mp.s, preferably 100 to 250 mp.s.

4. A process according to any one of claims 1 to 3, characterised in that the polyether polyol has a viscosity of from 30 to 1000mp.s, preferably from 50 to 500mp.s, at 25 ℃;

preferably, the polyether polyol has a functionality of 3, is polymerized from propylene oxide, and has a hydroxyl value of 80 to 800mgKOH/g, preferably 180 to 750mgKOH/g, more preferably 300 to 600 mgKOH/g.

5. The method according to any one of claims 1 to 4, wherein the catalyst comprises at least one heat-sensitive catalyst, and the activation temperature of the heat-sensitive catalyst is not lower than 50 ℃;

preferably, the catalyst comprises a heat-sensitive catalyst and at least one gel-type catalyst;

further preferably, the catalyst comprises only one heat-sensitive catalyst.

6. A process according to any one of claims 1 to 5, characterised in that the isocyanate-reactive component further comprises a small molecule alcohol;

the isocyanate-reactive component further comprises a flame retardant.

7. A process according to any one of claims 1 to 6, characterised in that, based on the total mass of the isocyanate-reactive components:

the using amount of the polyether polyol is 20-89.9%, preferably 45-84%;

the dosage of the catalyst is 0.1-0.7%, preferably 0.2-0.5%;

the dosage of the micromolecule alcohol is 0-30%, preferably 5-15%;

the amount of the flame retardant is 0-50%, preferably 10-40%.

8. A process according to any one of claims 1 to 7, characterised in that the molar ratio of isocyanate groups in the isocyanate component to active hydrogen atoms in the isocyanate-reactive component is from 0.85 to 1.25: 1, preferably 1 to 1.2: 1.

9. a method according to any one of claims 1 to 8, characterised in that the reinforcement material constitutes 10 to 90%, preferably 30 to 80%, of the total mass of the composite material.

10. The method according to any one of claims 1 to 9, wherein the preparation method adopts a high pressure resin transfer molding process comprising the steps of:

respectively and uniformly mixing and stirring the isocyanate components at 10-60 ℃ for later use, and uniformly mixing and stirring the isocyanate reactive components for later use;

and (2) uniformly mixing the isocyanate component and the isocyanate reactive component through a static mixer of high-pressure resin transfer molding equipment at the temperature of 10-60 ℃, injecting the mixture into a mold in which a reinforcing material is placed in advance, controlling the temperature of the mold to react at the temperature of 50-130 ℃, and obtaining the composite material after the reaction is finished.