This application claims priority to Chinese Patent Application Ser. No. CN2020103260788 filed on 23 Apr. 2020.

TECHNICAL FIELD

The present invention relates to a polyurethane polyol and a preparation method and application thereof. The polyurethane polyol is used for preparing a polyurethane elastomer.

BACKGROUND

Polyurethane is a polymer with a carbamate segment repetitive structure unit formed after the reaction of isocyanate and polyol. Polyurethane products are divided into foaming products and non-foaming products. The foaming products include soft, hard and semi-hard polyurethane foamed plastics. The non-foaming products include coatings, adhesives, synthetic leather, elastomers and elastic fibers. Polyurethane materials have excellent properties, wide applications and many kinds of products, among which the polyurethane foamed plastics is the most widely used.

There are three types of polyols used in the polyurethane, one is a polymer obtained by polymerization with epoxyethane, epoxypropane or epoxybutane by using polyol or organic amine as an initiator, which is called a polyether polyol; the other one is a modified grafted polyether polyol based on the polyether polyol and prepared by bulk polymerization of a vinyl monomer in polyol, which is called a polymer polyol, and is often used together with the polyether polyol; and the third one is a polyol polymerized by ring opening of tetrahydrofuran. However, with the decreasing reserves of petrochemical resources, the price of petrochemical products continues to rise and it is inconvenient to purchase the petrochemical products, which directly affects the production of products. Therefore, it is an important research orientation of polyols in recent years to seek a new resource that makes the products more economical and environmentally friendly, and reduces the dependence on the petrochemical products at the same time.

All the traditional elastomer polyether polyols use glycerine, diglycol and propylene glycol and other polyhydroxy compounds as initiators, and use epoxypropane and epoxyethane as chain extenders, among which more than 98% are petroleum derivatives. At present, people want to reduce dependence on petroleum and improve the environment. Compared with petroleum polyols, energy consumption of biomass polyols is reduced by 23%, non-renewable resources consumption of the biomass polyols is reduced by 61%, and greenhouse gas emissions of the biomass polyols is reduced by 36%. It has become an important development orientation of polyurethane materials to replace the petroleum polyols with the biomass polyols to produce polyurethane. As the cheapest and abundant vegetable oil, soybean oil is made into a soybean oil-based polyol by molecular modification, and may be used for synthesizing polyurethane. Polyurethane products produced thereby are not only safe and sanitary, but also show better mechanical properties, thermal stability and chemical resistance.

It is a common method to develop bio-based polyurethane polyol by using vegetable oil as a renewable raw material and using double bonds in a structure of the vegetable oil to transform hydroxyl functional groups. The vegetable oil is low in price and stable in source. Triglyceride and long chain groups thereof in the structure of the vegetable oil can replace petrochemical polyol. However, at present, the main problems in this field comprise the problems that the functional groups cannot be effectively transformed due to complicated raw material components and cross-linking side reactions easily caused by functional group transformation, as well as the problem that the foaming application is limited due to a wide distribution of molecular weights generated by cross-linking and a high viscosity of product. In addition, there is a multi-phase system in a reaction between the vegetable oil and multiple alcohol reagents, which has a low mass transfer efficiency. There is a contradiction between demands for an intensity and a time of the reaction and uncontrollable side reactions in the process, which greatly affects the product quality, so that a market potential of the product is limited. Meanwhile, the summary of a structure-activity relationship is not enough due to unclear product structure and uncontrollable process. Therefore, there is still much work to be done in this field, and many technical bottlenecks need to be broken. Developing new structures and adopting new reaction modes to realize effective control of the reaction process and accurate construction of the structure are the keys and difficulties in subsequent research and development. At the same time, the development of vegetable oil polyurethane polyol products has a broad market prospect, which will definitely break through the technical bottlenecks and break a breakthrough for the development of bio-based materials, and is expected to become a new economic growth point.

The application of the invention CN109369871A discloses a preparation method of a polyurethane polyol applied to a slow-rebound flexible polyurethane foam material, which includes the steps of preparing a hydroxyl compound from tris-(1-aziridinyl)phosphine oxide and other diols and halohydrins, and then carrying out ring-opening reaction on the hydroxyl compound and epoxy vegetable oil under the action of a catalyst to obtain a vegetable oil polyol. Halohydrin molecules are prone to cross-side reactions, and chlorine exists in by-products, which will also pollute the environment. Therefore, it is necessary to develop a new preparation process of the polyurethane polyol to solve problems thereof.

SUMMARY

Objective of the present invention: one technical problem to be solved by the present invention is to provide a polyurethane polyol aiming at the defects of the prior art, so as to overcome the problem that the current preparation of polyurethane polyol is depending on petrochemical resources, such that green and renewable epoxy vegetable oil resources can be introduced, and to prepare activity difference molecules with the same functional groups as much as possible on the basis of structure simulation and design, reduce cross-linking and decrease functionality utilization rate as much as possible, take economic effects into account, and construct a high-quality vegetable oil polyurethane polyol by using cheap reagents.

Another technical problem to be solved by the present invention is to provide a preparation method of the above polyurethane polyol aiming at the problems of crosslinking and high viscosity of products since the existing ring-opening reaction process of the epoxy vegetable oil is uncontrollable.

A final technical problem to be solved by the present invention is to provide an application of the above-mentioned polyurethane polyol.

In order to solve the above-mentioned problems, the present invention discloses a preparation method of a polyurethane polyol, which comprises the following steps of:

(1) dissolving 2,3-epoxybutane and an acid catalyst in an inert solvent to obtain a solution A; dissolving triethylene glycol in an inert solvent to obtain a solution B; and dissolving epoxy vegetable oil in an inert solvent to obtain a solution C;

(2) respectively and simultaneously pumping the solution A and the solution B into a first micromixer in a microchannel reaction device for mixing, and then introducing the mixture into a first microreactor for reaction to obtain a reaction solution containing a hydroxyl compound;

(3) respectively and simultaneously pumping the solution C and an effluent of the first microreactor into a second micromixer in the microchannel reaction device for mixing while carrying out step (2), and then introducing the mixture into a second microreactor for ring-opening reaction to obtain a reaction solution containing a vegetable oil polyol, and then separating the solution to obtain the vegetable oil polyol; and

(4) dissolving the vegetable oil polyol obtained in step (3) in an inert solvent to obtain a solution D; dissolving epoxypropane and an alkaline catalyst in an inert solvent to obtain a solution E; and respectively and simultaneously pumping the solution D and the solution E into a tank reactor for addition polymerization reaction, thereby obtaining the polyurethane polyol. A measure of controlling a flow rate and a concentration of reactants during pumping is employed to effectively avoid the occurrence of crosslinking.

In step (1), the acid catalyst is any one or combination of sulfuric acid, hydrochloric acid, phosphoric acid, fluoroboric acid, aluminum chloride and ferric chloride, and is preferably fluoroboric acid.

In step (1) and step (4), the inert solvent is any one or combination of dichloromethane, chloroform, carbon tetrachloride, dichloroethane and xylen, and is preferably dichloroethane.

In step (1), a molar ratio of the 2,3-epoxybutane to the acid catalyst in the solution A is (1.0 to 1.25):(0.1 to 0.2), and preferably 1:0.16; and a concentration of the 2,3-epoxybutane is 2.20 mmol/mL to 4.50 mmol/mL.

In step (1), a concentration of the triethylene glycol in the solution B is 1.20 mmol/mL to 3.0 mmol/mL.

In step (1), the epoxy vegetable oil in the solution C is an epoxy soybean oil or epoxy cotton oil prepared according to the method disclosed in CN104292187A, and an epoxy value of the epoxy vegetable oil is 6.0 to 6.7 (i.e., an epoxy content in each 100 g of epoxy resin is 6.0 to 6.7); and a concentration of the epoxy vegetable oil is 0.15 mmol/mL to 0.40 mmol/mL (concentration of epoxy soybean oil=(amount of substance of epoxy soybean oil substance)/(volume of epoxy soybean oil+volume of solvent)).

In step (2), the microchannel reaction device comprises a first feed pump, a second feed pump, a third feed pump, a first micromixer, a second micromixer, a first microreactor, a second microreactor and a receiver; the first feed pump and the second feed pump are connected to the first micromixer in a parallel manner through a pipeline, the first micromixer is connected with the first microreactor in series, a discharge port of the first microreactor and the third feed pump are connected to the second micromixer in a parallel manner, the second micromixer is sequentially connected with the second microreactor and the receiver in series, and the connection is implemented through a pipeline; the temperature is controlled by heating in an oil bath pan; and the pump is an accurate pump with low pulsation.

Models of the first micromixer and the second micromixer are preferably slit plate mixer LH25; and models of the first microreactor and the second microreactor are preferably Vapotech. The first microreactor and the second microreactor are both connected with a back pressure valve to prevent gasification.

In step (2), a pumping rate ratio of the solution A to the solution B is 1:0.6 to 3.5, a reaction temperature is 70° C. to 100° C. (preferably 80° C.), and a reaction residence time is 5 minutes to 10 minutes (preferably 7 minutes).

Preferably, a volume of the first microreactor is 2 mL to 20 mL (preferably 8 mL), a flow rate of pumping the solution A into the first micromixer is 0.2 mL/min to 1.0 mL/min (preferably 0.5 mL/min), and a flow rate of pumping the solution B into the first micromixer is 0.2 mL/min to 1.0 mL/min (preferably 0.5 mL/min).

In step (3), a pumping rate ratio of the effluent of the first microreactor to the solution C is controlled to be 1:0.5 to 2.0; preferably, a molar ratio of the triethylene glycol to the epoxy vegetable oil is controlled to be 3.2 to 3.75:1 while controlling the rate; a reaction temperature is 80° C. to 140° C. (preferably 120° C.), and a reaction residence time is 5 minutes to 15 minutes (preferably 10 minutes).

Preferably, a volume of the second microreactor is 4 mL to 60 mL (preferably 20 mL); and a flow rate of pumping the solution C into the second micromixer is 0.4 mL/min to 2.0 mL/min (preferably 1.0 mL/min).

In step (3), the separating is to stand an effluent of the second microreactor for stratification, collect an oleic phase, wash the oleic phase to neutrality, and then obtain the vegetable oil polyol by liquid separation and rotary evaporation.

In step (4), a concentration of vegetable oil polyol in the solution D is 0.10 mmol/mL to 0.25 mmol/mL in the solution E, a concentration of the epoxypropane is 3.0 mmol/mL to 6.50 mmol/mL, and a molar ratio of the epoxypropane to an epoxy group in the epoxy vegetable oil is 5 to 15:1 (preferably 10:1); and a mass percentage of the alkaline catalyst to the epoxy vegetable oil is 0.02% to 0.1% (preferably 0.8%).

Concentration of vegetable oil polyol=(mass of vegetable oil polyol)/(volume of vegetable oil polyol+volume of solvent); wherein, the mass of the vegetable oil polyol is calculated according to the dosage of the epoxy vegetable oil in raw materials.

In step (4), the alkaline catalyst is any one or a combination of caesium carbonate, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium bicarbonate, magnesium carbonate, triethylamine, pyridine and sodium methoxide, and is preferably caesium carbonate.

In step (5), a pumping rate ratio of the solution D to the solution E is 1.5 to 6.5:1; and the reaction is carried out at 80° C. to 150° C. (preferably 130° C.) for 2.5 hours to 3 hours.

Preferably, a flow rate of pumping the solution D into the tank reactor is 10.0 mL/min to 50.0 mL/min, and a flow rate of pumping the solution E into the tank reactor is 10.0 mL/min to 50.0 mL/min.

After the reaction in step (5) is finished, a product in the tank reactor is stood for stratification, and an oleic phase is collected and washed with an acid for neutralization until a pH value is 6.5 to 7.5, then liquid separation is carried out, and an organic phase is subjected to rotary evaporation, and then dried to obtain the polyurethane polyol; the acid is one or more of a hydrochloric acid, a sulfuric acid and a phosphoric acid, preferably a hydrochloric acid, and a mass percentage concentration of the hydrochloric acid is 5%.

The polyurethane polyol prepared by the above-mentioned method is also within the scope of protection of the present invention.

An application of the above-mentioned polyurethane polyol in preparing a polyurethane elastomer is also within the scope of protection of the present invention.

A preparation method of the polyurethane elastomer refers to the prior art, and a preferred method is as follows: under the protection of nitrogen, the polyurethane elastomer is prepared by a prepolymer method, the vegetable oil polyol prepared by the present invention is mixed with water, silicone oil, a cell-opening agent, a catalyst A-33, a catalyst A-1 and a catalyst T-12, and then 4,4′-diphenylmethane diisocyanate is added for reaction at 70° C. to 90° C. for 1.5 hours to 2.5 hours. A free NCO content in the reaction system is determined by a di-n-butylamine method, and then 1,4-butylene glycol is added according to a chain extension coefficient of 0.95. After stirring and mixing evenly, the mixture is poured into a flat steel mold at 90° C. to 120° C., vulcanized and aged for 20 hours to 30 hours in an oven at 80° C. to 100° C. A mass ratio of the vegetable oil polyol to the water, the silicone oil, the cell-opening agent, the catalyst A-33, the catalyst A-1 and the catalyst T-12 is 1:0.015 to 0.025:0.005 to 0.015:0.015 to 0.025:0.002 to 0.004:0.0005 to 0.0015:0.00005 to 0.00007. A mass ratio of the vegetable oil polyol to the 4,4′-diphenylmethane diisocyanate is 1:0.7 to 1.05.

Beneficial effects: compared with the prior art, the present invention has the following advantages.

(1) A microchannel technology is employed in the present invention to prepare the low-viscosity polyurethane polyol, which has good quality and light color, and may be completely replace a traditional polyether polyol for preparing a polyurethane elastomer without being mixed with a petrochemical polyether polyol. (2) The present invention has the advantages of simple process, convenient operation, low energy consumption, few side reactions, high reaction efficiency as well as stable and controllable process, and the obtained product does not need further treatment, and has engineering enlargement potential.

