CN101906192B - A kind of preparation method of aqueous polyurethane-acrylate composite emulsion - Google Patents

Abstract

The invention discloses a method for preparing an aqueous polyurethane-acrylate composite emulsion. In the absence of a metal catalyst and an organic solvent, a polymer diol, a diisocyanate, and a hydrophilic chain extender are used to synthesize an aqueous polyurethane prepolymer, and then the prepolymer is capped with a vinyl compound, followed by neutralization, water is added dropwise for self-emulsification, and then chain extension is performed to obtain an aqueous polyurethane dispersion. In the absence of an external emulsifier, an acrylate monomer dissolved in an initiator is added dropwise to the dispersion for polymerization to obtain an aqueous polyurethane-acrylate composite emulsion with a high solid content. The obtained composite emulsion has a solid content of more than 45%, and no solvent or metal catalyst is used in the preparation process, and no pollutants are discharged, which is a clean production process. The obtained aqueous environmentally friendly aqueous polyurethane-acrylate composite emulsion with a high solid content can be used as an adhesive, a coating, and the like.

Description

A kind of preparation method of aqueous polyurethane-acrylate composite emulsion

technical field

The invention relates to a preparation method of a polymer emulsion, in particular to a preparation method of an aqueous polyurethane-acrylate composite emulsion.

Background technique

Polyurethane is a kind of polymer material with excellent performance. It has the advantages of low temperature resistance, chemical corrosion resistance, friction resistance and good flexibility. It has been widely used as coatings, adhesives and fabric finishing agents. Traditional polyurethane materials are mainly solvent-based, and the organic solvents used generally have disadvantages such as flammability, explosion, strong smell, and toxicity, and are likely to cause harm to human health and the environment during production and use. Water-based polyurethane materials, which began to appear in the 1970s and developed rapidly, have the advantages of low toxicity, non-flammability, and low pollution compared with traditional solvent-based polyurethanes. With the continuous improvement of the performance of water-based polyurethane products, and the promulgation of relevant laws and regulations restricting the use of volatile organic compounds (VOC) in many countries and departments, the transformation from solvent-based polyurethane to water-based polyurethane has become inevitable.

However, while water-based polyurethane has many advantages such as excellent solvent resistance, abrasion resistance and flexibility, due to the introduction of hydrophilic groups in its own structure, there are defects such as poor water resistance and reduced surface gloss. Production costs are higher. Polyacrylate materials, which are widely used in the fields of coatings, adhesives, printing and dyeing, etc., have properties such as weather resistance, pollution resistance, acid resistance, alkali resistance, and good transparency, and the production cost is low, but there are also low temperature changes. Brittle, sticky at high temperature, poor solvent resistance, poor tensile properties and other shortcomings. Therefore, combining the two together by physical or chemical methods to prepare water-based polyurethane-acrylate composite emulsion not only reduces the production cost, but also combines the advantages of both to achieve complementary advantages and improve product performance.

At present, the waterborne polyurethane-acrylate composite emulsion reported in China has a low solid content, generally 30%~40%, and has a core-shell structure. In the preparation process, it is often necessary to use an organic solvent to dissolve the hydrophilic chain extender or reduce the polyurethane pre- Polymer viscosity, the final product needs to remove and recover the organic solvent. Without the use of organic solvents, the process of solvent removal and recovery can be omitted to improve production efficiency, and at the same time, it can avoid the harm to human health and the environment in the process of production and use, which is in line with the concept of clean production; on the other hand, high solid content emulsion It has the advantages of fast drying and good initial adhesion, and also reduces production, packaging and transportation costs. Therefore, the preparation of waterborne polyurethane-acrylate composite emulsions with high solid content (above 45%) without any solvent will have important practical application value, and related methods are rarely reported.

Contents of the invention

The purpose of the present invention is in order to overcome the shortcoming that exists in the present water-based polyurethane-acrylate composite emulsion preparation method, a kind of new preparation method is provided, this method can synthesize the water-based polyurethane-acrylate composite emulsion with high solid content without solvent.

The present invention is realized through the following technical solutions, comprising the steps of:

(1) Without any metal catalysts and solvents, use polymer diols, diisocyanates, and hydrophilic chain extenders to synthesize waterborne polyurethane prepolymers;

(2) Block the prepolymer with a vinyl compound, then neutralize, add water to self-emulsify, and extend the chain to obtain a water-based polyurethane dispersion;

(3) In the absence of an external emulsifier, the acrylate monomer dissolved in the initiator was added dropwise to the dispersion for polymerization to prepare a waterborne polyurethane-acrylate composite emulsion with high solid content.

The polymer diol is one or a mixture of polybutylene adipate (PBA) and polypropylene glycol (PPG).

The diisocyanate is a mixture of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) in a molar ratio of 2:1.

The hydrophilic chain extender is dimethylolbutyric acid (DMBA), which accounts for 3.2-4.0% of the mass of waterborne polyurethane. Dimethylolpropionic acid (DMPA) is a widely used hydrophilic chain extender in the synthesis of water-based polyurethane, but DMPA has a high melting point (175-185°C) and is difficult to dissolve by heating, which requires the addition of solvents such as N -formazol Nylpyrrolidone (NMP), acetone, etc. NMP has a high boiling point and is difficult to remove, while DMPA has low solubility in acetone, so a large amount of acetone needs to be added during the synthesis process, and the deketonization process is troublesome and unclean, which brings safety hazards to the production process. Dimethylolbutyric acid (DMBA) has a lower melting point than DMPA, and DMBA is easily soluble in polyols. Using DMBA as a hydrophilic chain extender can reduce or even eliminate the use of solvents for the prepolymerization of polyurethane.

In step (1), in the reaction system, the molar ratio of -NCO to -OH is 1.5 to 1.8, the -NCO is the total molar amount of isocyanate groups contained in HDI and IPDI, and the -OH is the The total molar weight of the hydroxyl groups contained in the alcohol and DMBA; the polyurethane prepolymer was synthesized at 80°C under nitrogen protection, and the reaction time was 3.5h.

In step (2), the vinyl compound is hydroxyethyl methacrylate, the temperature of the capping reaction is 70°C, and the time of the capping reaction is 1h; the neutralization reaction is carried out with triethylamine, and the temperature of the neutralization reaction is 60°C, the neutralization reaction time is 20min; the self-emulsifying water-based polyurethane pre-emulsion is obtained by adding water droplets into the prepolymer, the emulsification temperature is 60°C, the emulsification time is 20min, and the stirring speed is 400r/min; the obtained polyurethane pre-emulsion adopts The chain is extended with diamine aqueous solution, and the reaction temperature is 60°C.

In step (3), the initiator is azobisisobutyronitrile (AIBN), and the acrylate monomer is one or more of methyl methacrylate, butyl methacrylate, and butyl acrylate mixture, the temperature of the polymerization reaction is 79~90°C, and the polymerization reaction time is 7h.

The solid content of the aqueous polyurethane-acrylate composite emulsion prepared by the invention is higher than 45%, and the storage stability is greater than 12 months.

Compared with the prior art, the present invention has the following beneficial effects:

In the present invention, the commonly used DMPA is replaced by a new hydrophilic chain extender, DMBA, and the polyurethane prepolymer has an appropriate viscosity by controlling the molar ratio (R value) of -NCO to -OH, so that the synthesis process does not use any solvent, and does not use Organic solvents can save the process of solvent removal and recovery to improve production efficiency, and at the same time avoid the harm caused by human health and the environment in the process of production and use; do not use metal catalysts to avoid residual metal toxicity; do not use external emulsifiers It can improve the water resistance of the product; the solid content reaches 45%, which has the advantages of fast drying and good initial adhesion, and can also reduce production, packaging and transportation costs.

Detailed ways

The present invention is further explained below in conjunction with the examples, but the examples do not limit the present invention in any form.

Embodiment 1: the preparation of polyester type water-based polyurethane-acrylate composite emulsion

First put 25.6g of PBA in a 250mL three-necked flask, and remove water under vacuum at 120°C for 1h. Stop the vacuum, pass nitrogen, add 1.304g DMBA, and continue heating until it completely dissolves. Cool to 80°C, add 2.26mL IPDI and 3.46mL HDI, react at 80°C for 3.5h under stirring at 300 r/min to obtain a waterborne polyurethane prepolymer; cool down to 70°C, add 0.82 g of HEMA, and continue the reaction for 1h. Cool down to 60°C, add 0.85g TEA, and react for 20min. Add 63mL of water dropwise to the reaction system, stir and emulsify at 400r/min to obtain a pre-emulsion, dissolve 0.265g of EDA in 6.3mL of water and add dropwise to the above-mentioned pre-emulsion, react for 30min to obtain an aqueous polyurethane dispersion. Then, under stirring (300r/min) at 79°C, 22.68g of BA solution dissolved with 0.204g of AIBN was added dropwise to the above dispersion, and the drop was completed within 3h, and the reaction was continued for 2h. Raise the temperature to 82°C, react for 1 hour, then raise the temperature to 85°C, react for 45 minutes, then raise the temperature to 90°C, and react for 15 minutes. Cool to normal temperature and discharge. The obtained composite emulsion had a solid content of 45%, a viscosity of 52.8 cP, a film tensile strength of 13.9 MPa, an elongation at break of 1022.0%, a water absorption rate of 1.07% at 25°C for 24 hours, and a water absorption rate of 5.87% at 60°C for 36 hours. The average emulsion particle size is 87.5nm, and the storage stability is greater than 12 months.

Embodiment 2: the preparation of polyether type waterborne polyurethane-acrylic ester composite emulsion

According to the same preparation method as in Example 1, but 25.6g PBA is changed to 25.6g PPG, and 22.68g BA is changed to 22.68g MMA. The obtained composite emulsion has a solid content of 45%, a viscosity of 45.4cP, an average particle size of 138.9nm, a transparent film, a tensile strength of 14.2MPa, an elongation at break of 452.5%, and a 24h water absorption rate of 3.00% at 25°C. The water absorption rate at 60°C for 36 hours is 15.22%.

Embodiment 3: the preparation of polyester/polyether type waterborne polyurethane-acrylic ester composite emulsion

The same preparation method as in Example 1, but 25.6g PBA is changed into 20.48gPBA and 5.12gPPG. The obtained composite emulsion has a solid content of 45%, a viscosity of 93.2 cP, an average particle size of 93.1 nm, a tensile strength of 7.1 MPa, a breaking elongation of 882.8%, a water absorption rate of 1.91% at 25°C for 24 hours, and a water absorption rate of 60°C for 36 hours. The rate is 7.53%.

Claims (8)

1. the preparation method of an aqueous polyurethane-acrylate composite emulsion is characterized in that comprising the steps:

(1) under no any metal catalyst and solvent, adopts polymer diatomic alcohol, vulcabond, wetting ability chainextender synthetic water based polyurethane performed polymer;

(2) with vinyl compound performed polymer is carried out end-blocking, carry out self-emulsifying with post neutralization, dropping water, chain extension obtains aqueous pu dispersions then;

(3) in the presence of nothing adds emulsifying agent, drip the acrylic ester monomer that is dissolved with initiator in the dispersion-s and carry out polymerization, make the aqueous polyurethane-acrylate composite emulsion of high solids content;

Said wetting ability chainextender is a dimethylolpropionic acid, accounts for 3.2～4.0% of aqueous polyurethane performed polymer quality;

In the step (1); In the said reaction system;-NCO is 1.5～1.8 with the mol ratio of-OH; Said-NCO is the integral molar quantity of hexamethylene diisocyanate and the contained NCO of isophorone diisocyanate, and said-OH is the integral molar quantity of polymer diatomic alcohol and dimethylolpropionic acid institute hydroxyl.

2. preparation method as claimed in claim 1 is characterized in that said polymer diatomic alcohol is one or both the mixture in poly adipate succinic acid ester, the W 166.

3. preparation method as claimed in claim 1 is characterized in that said vulcabond is the mixture that hexamethylene diisocyanate and isophorone diisocyanate were formed in 2: 1 in molar ratio.

4. preparation method as claimed in claim 1 is characterized in that in the step (1), said base polyurethane prepolymer for use as synthesizes under the nitrogen protection at 80 ℃, and the reaction times is 3.5 hours.

5. preparation method as claimed in claim 1 is characterized in that in the step (2), said vinyl compound is a Rocryl 400, and the temperature of end capping is 70 ℃, and the end capping time is 1 hour.

6. preparation method as claimed in claim 1 is characterized in that in the step (2), and said neutralization is carried out neutralization reaction for adopting triethylamine, and the temperature of neutralization reaction is 60 ℃, and the neutralization reaction time is 20 minutes.

7. preparation method as claimed in claim 1 is characterized in that in the step (2), and said chain extension carries out chain extending reaction for adopting quadrol, and the temperature of chain extending reaction is 60 ℃, and the chain extending reaction time is 30 minutes.

8. preparation method as claimed in claim 1; It is characterized in that in the step (3); Said initiator is a Diisopropyl azodicarboxylate; Acrylic ester monomer is one or more the mixture in TEB 3K, NSC 20956, the Bing Xisuandingzhi, and the temperature of polyreaction is 79～90 ℃, and polymerization reaction time is 7 hours.