Natural latex polyether polyols, their preparation methods and applications

Abstract

This invention belongs to the field of polyether polyol preparation technology, specifically relating to a natural latex polyether polyol, its preparation method, and its application. The natural latex polyether polyol is obtained by polymerization of epoxidized natural latex and small molecule alcohols / amines as composite initiators under the action of an alkaline catalyst with epoxides; the epoxidized natural latex is obtained by epoxidation modification of natural latex with formic acid and 30 wt.% hydrogen peroxide. The natural latex polyether polyol of this invention is prepared by polymerization using epoxidized natural latex with introduced active epoxy groups and small molecule alcohols / amines as composite initiators. Utilizing the unique toughness of its rubber phase structure, and with the optimization of the reactivity between the polyether polyol and isocyanates through epoxidation modification, its application in polyurethane materials results in polyurethane flexible foam products with good mechanical properties, excellent resilience, and a pleasant feel. This invention also provides its preparation method.

Description

Technical Field

[0001] This invention belongs to the field of polyether polyol preparation technology, specifically relating to a natural latex polyether polyol, its preparation method, and its application. Background Technology

[0002] Polyether polyols, with their tunable molecular structure and excellent properties, are widely used in various polyurethane materials, including rigid polyurethane foam and flexible polyurethane foam, playing an irreplaceable role in building insulation, furniture manufacturing, automotive interiors, and cold chain packaging. However, existing rigid polyurethane foams made from polyether polyols often suffer from insufficient toughness and brittleness, affecting their long-term stability in insulation projects and other applications. Meanwhile, flexible polyurethane foams face challenges such as difficulty in controlling hardness and poor durability.

[0003] Natural latex is a viscous, milky-white, emulsion-like aqueous dispersion, resembling milk in appearance. Its core is a stable dispersion system of rubber particles in a near-neutral medium. The main component of these rubber particles is cis-1,4-polyisoprene (a natural polymer compound), with rubber hydrocarbon (cis-1,4-polyisoprene) accounting for 91%-94% by mass. The remainder consists of non-rubber components such as proteins, fatty acids, ash, and sugars. As the most widely used general-purpose rubber material, natural latex has significant application value in multiple industrial fields due to its excellent elasticity, adhesion, and biocompatibility.

[0004] However, due to the special structure of natural latex, the aldehyde groups on the molecular chain are prone to condensation reactions, leading to viscosity changes during storage. Furthermore, its compatibility and reactivity with epoxides are difficult to control. Therefore, natural latex is usually only used in rubber products and has poor applicability in polyurethane materials.

[0005] CN118667241A discloses a polyurethane / natural latex blended foamed product and its preparation method. The product formulation includes natural latex, polyurethane emulsion modified with collagen or soy protein, vulcanizing agent, additives, and fillers such as silica sol. Blending polyurethane with natural latex can improve the mechanical stability and mechanical properties of the product. The protein modifier increases the cross-linking structure through grafting reaction, and optimization methods such as enzyme-modified soy protein and polysaccharide grafting further enhance the mechanical strength. At the same time, it endows the product with excellent antibacterial and antioxidant properties. This method obtains the product by blending and foaming modified polyurethane with natural latex, which utilizes the advantages of polyurethane and natural latex and improves the performance of the product. However, this technology only physically mixes and foams polyurethane and natural latex. The natural latex molecules and polyurethane molecules cannot be organically combined, and the improvement of the mechanical properties and mechanical strength of the product is limited. Summary of the Invention

[0006] To overcome the aforementioned deficiencies in existing technologies, this invention provides a natural latex polyether polyol, prepared by polymerization using natural latex with active epoxy groups introduced through epoxidation modification and small molecule alcohols / amines as composite initiators. Utilizing the unique toughness of its rubber phase structure, and with the optimization of the reactivity between the polyether polyol and isocyanate through epoxidation modification, this polyether polyol is applied to polyurethane materials, resulting in polyurethane flexible foam products with excellent mechanical properties, superior resilience, and a pleasant feel. This invention also provides a method for its preparation.

[0007] The natural latex polyether polyol of the present invention is obtained by polymerizing epoxidized natural latex and small molecule alcohol / amine as composite initiators under the action of an alkaline catalyst with epoxide alkane; wherein, the epoxidized natural latex is obtained by epoxidation modification of natural latex with formic acid and 30 wt.% hydrogen peroxide.

[0008] The specific preparation process of the epoxidized natural rubber latex is as follows: 20 wt.% of polyoxyethylene laurate ether aqueous solution is added to the natural rubber latex diluted with water, and after stirring for 1-2 hours, formic acid and 30 wt.% hydrogen peroxide are added. The temperature is controlled at 30-60℃, and the reaction time is 6-20 hours to obtain the epoxidized natural rubber latex; wherein, the mass ratio of natural rubber latex, formic acid and 30 wt.% hydrogen peroxide is 4:(1-2):(2-4), and the natural rubber latex is calculated based on its effective solids content.

[0009] The solid content of the natural latex is 40-70 wt.%, preferably the natural latex from Shandong Feihong New Material Co., Ltd., which has a solid content of 60 wt.%, and the dilution ratio with water is 50% of the original solid content. The amount of polyoxyethylene laurate ether aqueous solution used is 1.5-5.0 wt. of the effective solid content of the natural latex.

[0010] The alkaline catalyst is one of 2,4,6-tris(dimethylaminomethyl)phenol, trimethylamine, triethylamine, and triethanolamine.

[0011] The small molecule alcohol / amine mentioned is one of diethanolamine, glycerol, or monoethanolamine.

[0012] The epoxide is one or both of propylene oxide and ethylene oxide, preferably propylene oxide.

[0013] The mass ratio of the epoxidized natural rubber latex, small molecule alcohol / alkanolamine, and epoxide is 1:(0.05-0.5):(0.5-3), preferably 1:(0.15-0.3):(1-2); the amount of alkali catalyst added is 0.1-3 wt.% of the total amount of composite initiator and epoxide, preferably 1-2 wt.%.

[0014] The preparation method of the natural latex polyether polyol includes the following steps: adding epoxidized natural latex and small molecule alcohol / amine into a reaction vessel, adding an alkaline catalyst, performing nitrogen purging, performing a pressure test on the polymerization reaction vessel to ensure good sealing, controlling the pressure to -0.08~-0.1MPa and the temperature to 80-85℃, adding epoxide alkane, maintaining the pressure and temperature after feeding, continuing to mature for 0.5-2h, and finally, raising the temperature to 100-120℃, removing unreacted monomers under vacuum until the moisture content is <0.1wt.%, to obtain the natural latex polyether polyol.

[0015] The application of the aforementioned natural latex polyether polyol is to use it in the preparation of rigid polyurethane foam materials or flexible polyurethane foam materials. Specifically, it can be used as a raw material for polyurethane slow rebound foam, high rebound foam, and polyurethane spray insulation materials.

[0016] This invention introduces natural latex into the polyurethane structure, using natural latex biomaterials in the preparation of polyurethane foam. This solves the problem that natural latex cannot react with isocyanates. Since natural latex molecules lack functional groups that react with isocyanates, its double bond structure is utilized to form epoxy groups through epoxidation modification. These epoxy groups can react with small-molecule alcohols / alkanolamines to form large-molecule alcohols / alkanolamines, which then react with propylene oxide and ethylene oxide to form polyether polyols. The polyether polyols then react with isocyanates to ultimately form polyurethane materials containing natural latex. The epoxidation modification of natural latex introduces epoxy groups, which are then converted into active groups and integrated into the polyurethane crosslinking network. This improves the brittleness and fracture toughness of rigid polyurethane foam and enhances the support of the crosslinking network in flexible foam, thereby increasing compressive strength. Furthermore, natural latex is a bio-based material, making its integration into polyurethane environmentally friendly.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The natural latex polyether polyol of the present invention uses epoxidized natural latex as an initiator to prepare polyether polyol. The polyether polyol has both the toughness of the natural latex rubber phase and the reactivity of polyether polyol, which solves the problem of insufficient toughness of traditional polyether polyol and effectively expands the application range of natural latex.

[0019] (2) The method for preparing natural latex polyether polyol of the present invention introduces active sites into natural latex through epoxidation modification, and constructs a composite initiator system by combining small molecule alcohol / alkanolamine. The process conditions are mild and easy to control, realizing the conversion of natural latex bio-based materials. The preparation process is simple.

[0020] (3) The natural latex polyether polyol of the present invention is applied to polyurethane materials. The natural latex is epoxidized to introduce epoxy groups and convert them into active groups that are connected to the polyurethane crosslinking network. By utilizing the unique toughness of its rubber phase structure, it can effectively enhance the compressive strength of polyurethane soft foam, so that the polyurethane soft foam product has good mechanical properties, excellent resilience and hand feel. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments and comparative examples. Unless otherwise specified, the raw materials used in the embodiments and comparative examples are all conventional commercial raw materials, and the process methods used are all conventional methods in the art unless otherwise specified. The parts involved in the raw materials in the embodiments and comparative examples are all parts by mass. Unless otherwise specified, the raw material ratios are all by mass, and the natural latex is calculated based on the effective solids content.

[0022] The raw materials are described below:

[0023] Natural latex: solid content 60 wt.%, Shandong Feihong New Materials Co., Ltd.;

[0024] INOVOL C310: Hydroxyl value 168mgKOH / g, Shandong Yinuowei New Materials Co., Ltd.;

[0025] INOVOL C220: 56mgKOH / g, Shandong Yinuowei New Materials Co., Ltd.;

[0026] L 580: Momentive Advanced Materials Group;

[0027] DG 5412: Shandong Yinuowei Polyurethane Co., Ltd.

[0028] The specific preparation process of the epoxidized natural latex is as follows:

[0029] Natural latex with a solid content of 60 wt.% was diluted with water to 50% of its original solid content. Then, 20 wt.% of polyoxyethylene laurate ether aqueous solution (1.5-5.0 wt.% of the effective solid content of natural latex) was added. After stirring for 1-2 hours, formic acid and 30 wt.% hydrogen peroxide were added. The temperature was controlled at 30-60℃ and the reaction time was 6-20 hours to obtain epoxidized natural latex. The mass ratio of natural latex, formic acid and 30 wt.% hydrogen peroxide was 4:(1-2):(2-4).

[0030] The preparation method of the natural latex polyether polyol includes the following steps:

[0031] Epoxidized natural rubber latex and small molecule alcohols / amines were added to a reactor, along with an alkaline catalyst. Nitrogen purging was performed, and the reactor was pressure-tested to ensure good sealing. The pressure was controlled at -0.08 to -0.1 MPa and the temperature at 80-85°C. Propylene oxide was added, and after feeding was complete, the pressure and temperature were maintained for further maturation for 0.5-2 hours. Finally, the temperature was raised to 100-120°C, and unreacted monomers were removed under vacuum to obtain natural rubber latex polyether polyol. The mass ratio of epoxidized natural rubber latex, small molecule alcohols / amines, and propylene oxide was 1:(0.15-0.3):(1-2). The amount of alkaline catalyst added was 1-2 wt.% of the total amount of the composite initiator and epoxides.

[0032] Example 1

[0033] The specific preparation process of the epoxidized natural latex is as follows:

[0034] 100g of natural latex with a solid content of 60wt.% was diluted with water to 50% of its original solid content. Then, 2g of 20wt.% polyoxyethylene laurate ether aqueous solution was added and stirred for 1.5h. Then, 15g of formic acid and 30g of 30wt.% hydrogen peroxide were added. The temperature was controlled at 60℃ and the reaction time was 12h to obtain epoxidized natural latex.

[0035] The preparation method of the natural latex polyether polyol includes the following steps:

[0036] 100g of epoxidized natural rubber latex and 30g of diethanolamine were added to the reactor, followed by 6g of 2,4,6-tris(dimethylaminomethyl)phenol. Nitrogen purging was performed, and the polymerization reactor was pressure tested to ensure good sealing. The pressure was controlled at -0.1MPa and the temperature at 80℃. 200g of propylene oxide was added, and the pressure and temperature were maintained after feeding. The mixture was allowed to mature for another 0.5h. Finally, the temperature was raised to 110℃, and unreacted monomers were removed under vacuum until the moisture content was <0.1wt.%, yielding natural rubber latex polyether polyol.

[0037] Example 2

[0038] The specific preparation process of the epoxidized natural latex is as follows:

[0039] 100g of natural latex with a solid content of 60wt.% was diluted with water to 50% of its original solid content. Then, 0.9g of 20wt.% polyoxyethylene laurate ether aqueous solution was added and stirred for 1h. Then, 30g of formic acid and 60g of 30wt.% hydrogen peroxide were added. The temperature was controlled at 50℃ and the reaction time was 6h to obtain epoxidized natural latex.

[0040] The preparation method of the natural latex polyether polyol includes the following steps:

[0041] 150g of epoxidized natural rubber latex and 30g of glycerol were added to the reactor, followed by 6g of triethylamine. Nitrogen was used for purging, and the polymerization reactor was pressure tested to ensure good sealing. The pressure was controlled at -0.08MPa and the temperature at 85℃. 200g of propylene oxide was added, and the pressure and temperature were maintained after feeding. The mixture was allowed to mature for another hour. Finally, the temperature was raised to 100℃, and unreacted monomers were removed under vacuum until the moisture content was <0.1wt.%, yielding natural rubber latex polyether polyol.

[0042] Example 3

[0043] The specific preparation process of the epoxidized natural latex is as follows:

[0044] 100g of natural latex with a solid content of 60wt.% was diluted with water to 50% of its original solid content. Then, 3g of 20wt.% polyoxyethylene laurate ether aqueous solution was added and stirred for 1h. Then, 22.5g of formic acid and 45g of 30wt.% hydrogen peroxide were added. The temperature was controlled at 30℃ and the reaction time was 20h to obtain epoxidized natural latex.

[0045] The preparation method of the natural latex polyether polyol includes the following steps:

[0046] 200g of epoxidized natural rubber latex and 30g of monoethanolamine were added to the reactor, followed by 6g of triethanolamine. Nitrogen was used for purging, and the polymerization reactor was pressure tested to ensure good sealing. The pressure was controlled at -0.093MPa and the temperature at 85℃. 200g of propylene oxide was added, and the pressure and temperature were maintained after feeding. The mixture was allowed to mature for another 2 hours. Finally, the temperature was raised to 120℃, and unreacted monomers were removed under vacuum until the moisture content was <0.1wt.%, yielding natural rubber latex polyether polyol.

[0047] Comparative Example 1

[0048] The preparation method of the natural latex polyether polyol includes the following steps:

[0049] 100g of natural latex and 30g of diethanolamine were added to the reactor, followed by 6g of 2,4,6-tris(dimethylaminomethyl)phenol. Nitrogen purging was performed, and the polymerization reactor was pressure tested to ensure good sealing. The pressure was controlled at -0.1MPa and the temperature at 80℃. 200g of propylene oxide was added, and the pressure and temperature were maintained after feeding. The mixture was allowed to mature for another 0.5h. Finally, the temperature was raised to 110℃, and unreacted monomers were removed under vacuum until the moisture content was <0.1wt.%, yielding polyether polyol.

[0050] The properties of the polyether polyols obtained in the above embodiments and comparative examples are shown in Table 1 below.

[0051] Table 1. Indicators of polyether polyols prepared in the examples and comparative examples.

[0052]

[0053] Example 1 The polyether polyol product prepared in Comparative Example 3 and Comparative Example 1 (denoted as polyether polyol 1) was used as raw material to prepare latex-like polyurethane flexible foam. In Comparative Example 2, INOVOL C310 polyether polyol was used to replace natural latex polyether polyol. The specific formulation by mass parts is shown in Table 2 below.

[0054] Table 2. Specific Example and Comparative Example Proportions

[0055]

[0056] The performance of the polyurethane flexible foams prepared in Examples 1-3 and Comparative Examples 1-2 was evaluated. Tensile strength was tested according to standard GB / T6344-2008; tear strength was tested according to standard GB / T10808-2006; and resilience was tested according to standard GB / T6670-2008. Using the feel of natural latex sponge samples as a standard, 30 people were randomly selected to conduct subjective evaluations of the polyurethane foam products prepared in the examples and comparative examples. Excellent indicates that the feel of the tested foam is the same as that of the natural latex sponge sample and is difficult to distinguish; Good indicates that the feel of the tested foam is close to that of latex sponge; Poor indicates that the feel of the tested foam is significantly different from that of latex sponge. The test results are shown in Table 3.

[0057] Table 3. Performance test results of polyurethane flexible foam

[0058]

[0059] As shown in Table 3, the polyether polyol prepared in Comparative Example 1 had an abnormally high hydroxyl value (500 mg KOH / g) and no effective viscosity data was measured. Therefore, it could not be used to prepare polyurethane products. The reason is that natural latex lacks functional groups that can participate in the reaction, leading to an abnormal polyether polyol structure that cannot react with isocyanate. Comparative Example 2 used the traditional polyether polyol INOVOL C310 to replace the natural latex polyether polyol. INOVOL C310's molecular chain is mainly composed of polyether bonds, with a regular structure but insufficient flexibility. It lacks the rubber phase structure unique to natural latex and has a low crosslinking network density, making the foam prone to structural damage under stress, resulting in low tensile and tear strength and insufficient resilience.

[0060] The natural latex polyether polyol of this invention produces a latex-like polyurethane flexible foam. After epoxidation modification, epoxy groups are introduced into the natural latex, forming a composite initiator with small molecule alcohols / amines. The resulting polyether polyol, polymerized with epoxides, has a more uniform distribution of active groups and forms a denser, more stable cross-linked network when reacting with isocyanates. This results in excellent mechanical properties. The rubber phase structure of natural latex possesses a unique soft touch and elasticity. By chemically polymerizing it into the polyurethane molecular chain, the foam retains the tactile characteristics of natural latex, with a feel close to that of natural latex sponge. Compared to latex-free polyurethane flexible foam, its overall performance is significantly improved.

Claims

1. A natural latex polyether polyol, characterized in that, The product is obtained by polymerizing epoxidized natural latex and small molecule alcohols / amines with epoxides under the action of an alkaline catalyst; wherein, the epoxidized natural latex is obtained by epoxidation modification of natural latex with formic acid and 30 wt.% hydrogen peroxide; The preparation method of natural latex polyether polyol includes the following steps: adding epoxidized natural latex and small molecule alcohol / amine into a reaction vessel, adding an alkaline catalyst, performing nitrogen purging, and performing a pressure test on the polymerization reaction vessel to ensure good sealing. The pressure is controlled at -0.08 to -0.1 MPa and the temperature at 80-85℃. Epoxy alkane is added, and after feeding is complete, the pressure and temperature are maintained for continued maturation for 0.5-2 hours. Finally, the temperature is raised to 100-120℃, and unreacted monomers are removed under vacuum until the moisture content is <0.1 wt.%, yielding natural latex polyether polyol; the epoxy alkane is one or both of propylene oxide or ethylene oxide.

2. The natural latex polyether polyol according to claim 1, characterized in that, The specific preparation process of the epoxidized natural latex is as follows: 20 wt.% of polyoxyethylene laurate ether aqueous solution is added to the natural latex diluted with water, and after stirring for 1-2 hours, formic acid and 30 wt.% of hydrogen peroxide are added. The temperature is controlled at 30-60℃ and the reaction time is 6-20 hours to obtain the epoxidized natural latex.

3. The natural latex polyether polyol according to claim 2, characterized in that, The solid content of the natural latex is 40-70 wt.%, and the dilution ratio with water is 50% of the original solid content. The amount of polyoxyethylene laurate ether aqueous solution used is 1.5-5.0 wt. of the effective solid content of the natural latex.

4. The natural latex polyether polyol according to claim 1, characterized in that, The mass ratio of natural latex, formic acid, and 30 wt.% hydrogen peroxide is 4:(1-2):(2-4).

5. The natural latex polyether polyol according to claim 1, characterized in that, The alkaline catalyst is one of 2,4,6-tris(dimethylaminomethyl)phenol, trimethylamine, triethylamine, and triethanolamine.

6. The natural latex polyether polyol according to claim 1, characterized in that, The small molecule alcohol / amine mentioned is one of diethanolamine, glycerol, and monoethanolamine.

7. The natural latex polyether polyol according to claim 1, characterized in that, The mass ratio of epoxidized natural rubber latex, small molecule alcohol / alkanolamine, and epoxide is 1:(0.05-0.5):(0.5-3); the amount of alkali catalyst added is 0.1-3 wt.% of the total amount of composite initiator and epoxide.

8. The application of the natural latex polyether polyol according to any one of claims 1-7, characterized in that, It is applied to the preparation of rigid polyurethane foam or flexible polyurethane foam.

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