CN1982351A - Production of NDI-polyurethane microporous elastomer - Google Patents

Abstract

The invention discloses a preparation method of an NDI-based polyurethane microcellular elastomer, aiming at solving the technical problem of poor weather resistance of the polyurethane microcellular elastomer in the prior art, especially the poor hydrolysis stability. The preparation method of the present invention comprises the following steps: (1) preparation of prepolymer: excess polyisocyanate reacts with polyol at 120-140°C to form a prepolymer with terminal-NCO groups; (2) casting: pouring The prepolymer and the chain extender components are mixed in proportion, and the reaction liquid is injected into the mold at a temperature of 80-95°C, and demolded after pre-curing; (3) post-curing: the demoulded product is post-cured at 110°C for 13 -16 hours. The product prepared by the method of the invention is used as a high-strength damping element that bears dynamic fatigue, such as a buffer shock-absorbing element of vehicles such as automobiles, a bridge shock-absorbing block, and the like.

Description

Preparation method of NDI-based polyurethane microcellular elastomer

technical field

The invention relates to a preparation method of a polyurethane microporous elastomer, in particular to the technical improvement of optimizing the hydrolysis resistance of the product.

Background technique

Due to the excellent static and dynamic mechanical properties of polyurethane microcellular elastomers, it is especially used in rocking vibration and damping systems. Their industrial importance is due to the combination of their good mechanical properties and cheap and convenient processing methods. Using various chemical structural components in different mixing ratios can produce products with widely different mechanical properties and processability. As we all know, 1.5-NDI-based microcellular elastomers have excellent performance, and have advantages that other isocyanate-based products cannot match in terms of dynamic fatigue performance and fatigue deformation performance, so they have been used as high-end products in special fields. In the usual preparation method, common polyalkylene polyol esters such as: poly(1.4-butylene glycol adipate) ester, poly(ethylene glycol adipate) ester are generally used as the main polyol components, However, the product has the disadvantages of poor weather resistance, especially insufficient hydrolytic stability, which affects the service life of the product. In order to overcome the above-mentioned shortcomings, the usual method is to add a certain amount of hydrolysis stabilizer, but this method will increase the manufacturing cost; in addition, technically speaking, polyesters formed by relatively long-chain diols and acids can also be used, or Polycaprolactone, etc., the disadvantages of this method are that this type of polyester has a high melting point, there is a risk of crystallization in the processing process, the production process has poor tolerance, and there are also disadvantages such as high hardness of the product.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and propose a method for preparing polyurethane microcellular elastomers to solve the problem of NDI-based microcellular elastomers’ weather resistance, especially insufficient hydrolytic stability, thereby prolonging the use of high-end products life.

In order to realize the above-mentioned object of the invention, the preparation method that the present invention proposes comprises the following steps:

(1) Preparation of prepolymer: Excessive polyisocyanate reacts with polyol at 120-140°C to form a prepolymer with terminal-NCO groups;

(2) Casting: Mix the prepolymer and chain extender components in proportion, inject the reaction liquid into a mold with a temperature of 80-95°C, and demould after pre-curing;

(3) Post-curing: post-curing for 13-16 hours at 110° C. after demoulding.

The polyisocyanate described in the above step (1) of the present invention is NDI (1.5-naphthalene diisocyanate);

The polyol described in the above-mentioned step (1) of the present invention is polyester polyol, generally selects the polyol ester that contains side group for use, as:, the polyester polyol that contains side methyl group is selected from poly(3-methyl-1.7 -octanediol adipate, poly(3-methylpentylene adipate), poly(β-methyl-δ-valerolactone) and poly(2-methyl-1.3 propanediol-1.4 -Butanediol adipate, poly(2-methyl-1.3 propanediol-1.4-butanediol-ethylene glycol adipate), poly(trimethylolpropane-2-methyl-1.3 propanediol -1.4-Butanediol adipate) ester, poly(1,3 dimethyl-1.3 propanediol-1.4-butanediol-ethylene glycol adipate) ester, poly(1,2-dimethylpropanediol- 1. 4-Butanediol-ethylene glycol adipate) etc.

Due to the presence of side methyl groups, the hydrophobicity of this type of polyester polyol is improved, and because of its non-crystalline nature, the product is balanced in terms of strength, elongation, flexibility and water resistance. In view of the fact that this type of polyester is obviously superior to polycaprolactone polyols with good water resistance in terms of cost and process stability, considering various factors, the polyols described in the above steps are preferably polyester polyols containing pendant methyl groups. Alcohol, more preferably a polyester polyol with a molecular weight of 1000-3500 and a functionality of 2-3 containing side methyl groups.

In the above step (2) of the present invention, the chain extender component is the same polyester component as the polyester polyol described in step (1) including components such as catalyst, foaming agent and surfactant mixture. The catalyst is mainly tertiary amine catalyst, such as: Dabco 33Lv; the surfactant is a non-ionic surfactant, such as DC 193, and an emulsifier such as castor oil sulfuric acid or fatty acid sodium salt can also be used; the foaming agent is water.

The mixing ratio described in the above step (2) of the present invention is 100:8-15.

The invention adopts a low-pressure foaming machine to realize the metering and mixing of prepolymer and crosslinking agent components.

Compared with the prior art, the preparation method of the present invention contains polyester polyols with side methyl groups, which obviously optimizes the hydrolysis resistance of the product; the product prepared according to the method of the present invention is used as a high-strength damping element that withstands dynamic fatigue such as an automobile Buffer shock absorbing components and bridge shock absorbing blocks for vehicles such as vehicles.

Description of drawings

Fig. 1 is a schematic structural view of the microcellular elastomer molded article used for testing the hydrolysis resistance of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Comparative Example 1

Poly(ethylene glycol-adipate) ester with a molecular weight of 2000 reacts with NDI at 120-140°C to obtain a prepolymer with a -NCO content of 6.25%; the crosslinking agent component is mainly polyester, and the auxiliary Agent components include foaming agent, catalyst, surfactant, etc., wherein the auxiliary component accounts for 15% of the total amount of crosslinking agent; using a low-pressure foaming machine, according to the ratio of isocyanate index to 100%, mix the prepolymer and For the cross-linking agent component, inject the reaction material liquid into a mold at 65-90°C to manufacture microporous elastomer products and test pieces, remove the mold after 30 minutes, and then put it into an oven at 110°C for post-aging for 15 hours.

The test piece prepared according to this embodiment was placed at room temperature for one week, and then its mechanical properties and hydrolysis resistance were measured.

Test static mechanical properties Samples are taken from a test piece of 155×75×20mm, and the test items include: tensile strength and elongation at break after normal and wet aging.

The test of hydrolysis resistance was taken from a cylindrical microporous elastomer molding with a height of 80 mm, an outer diameter of 50 mm, and an inner diameter of 16 mm. There are 2 neck-shaped constrictions on the cylinder (as shown in Figure 1). The product is compressed by 50%, soaked in water at 80°C, and the time for cracking or powdering on the surface of the product is observed, which is characterized by the boiling time.

The test results are shown in Table 1.

Comparative Example 2

Polycaprolactone ester with a molecular weight of 2000 and NDI are reacted at 120-140°C to obtain a prepolymer with an -NCO content of 4.18%; the crosslinking agent component is mainly polycaprolactone, and the auxiliary components include Foaming agent, catalyst, surfactant, etc., in which the auxiliary component accounts for 15% of the total crosslinking agent; using a low-pressure foaming machine, the prepolymer and the crosslinking agent are mixed according to the ratio of the isocyanate index to 100%. After 3 minutes, inject the reaction material liquid into a mold at 65-90°C to make a microporous elastomer test piece, demould after 30 minutes, and then put it into an oven at 110°C for post-aging for 15 hours.

The test piece prepared according to this embodiment was placed at room temperature for one week, and then its mechanical properties and hydrolysis resistance were measured.

Test mechanical properties with comparative example 1.

Test the hydrolysis resistance performance with comparative example 1.

The test results are shown in Table 1.

Example 1

Poly(trimethylolpropane-2-methyl-1.3propylene glycol-1.4-butanediol adipate) ester with a molecular weight of 3000 and a functionality of 2.3 reacts with NDI at 120-140°C to obtain -NCO content 8.2% prepolymer. The crosslinking agent component is mainly polyester, and the auxiliary component includes foaming agent, catalyst, surfactant, etc., wherein the auxiliary component accounts for 15% of the total crosslinking agent; using a low-pressure foaming machine, according to isocyanate The ratio of the index is 100%, mix the prepolymer and crosslinking agent components, inject the reaction material liquid into the mold at 65-90°C to make the microporous elastomer test piece, demould after 30min, and then put it into the oven at 110°C Post-cure for 15 hours.

The test piece prepared according to this embodiment was placed at room temperature for one week, and then its mechanical properties and hydrolysis resistance were measured.

Test mechanical properties with comparative example 1.

Test the hydrolysis resistance performance with comparative example 1.

The test results are shown in Table 1.

Example 2

Poly(1,2-dimethylpropanediol-1.4-butylene glycol-ethylene glycol adipate) ester with a molecular weight of 2000 reacts with NDI at 120-140°C to obtain a prepolymer with a -NCO content of 6.50%. body. The crosslinking agent component is mainly polyester, and the auxiliary component includes foaming agent, catalyst, surfactant, etc., wherein the auxiliary component accounts for 15% of the total crosslinking agent; using a low-pressure foaming machine, according to isocyanate The ratio of the index is 100%, mix the prepolymer and crosslinking agent components, inject the reaction material liquid into the mold at 65-90°C to make the microporous elastomer test piece, demould after 30min, and then put it into the oven at 110°C Post-cure for 15 hours.

The test piece prepared according to this embodiment was placed at room temperature for one week, and then its mechanical properties and hydrolysis resistance were measured.

Test mechanical properties with comparative example 1.

Test the hydrolysis resistance performance with comparative example 1.

The test results are shown in Table 1.

Table 1: Static mechanical properties and hydrolysis resistance of the microcellular elastomers prepared in Comparative Example 1-2 and Example 1-2

serial number project Comparative Example 1 Comparative Example 2 Example 1 Example 2 1 Overall density Kg/m ³ 420 425 428 418 2 Tensile strength Mpa Normal 4.10 4.78 4.52 4.32 After wet aging 3.20 4.32 3.90 3.86 Change rate % 22.0 9.6 13.7 10.5 3 Elongation at break% Normal 490 475 427 440 After wet aging 469 458 415 425 Change rate % 4.3 3.6 2.8 3.4 4 Boiling time hours 680 1620 1540 1260

Claims (12)

1, a kind of preparation method of NDI base polyurethane microcellular elastomer, it is characterized in that this preparation method comprises the steps: (1) Preparation of prepolymer: Excessive polyisocyanate reacts with polyol at 120-140°C to form a prepolymer with terminal-NCO groups; (2) Casting: Mix the prepolymer and chain extender components in proportion, inject the reaction liquid into a mold with a temperature of 80-95°C, and demould after pre-curing; (3) Post-curing: post-curing for 13-16 hours at 110° C. after demoulding. 2. The preparation method of NDI-based polyurethane microcellular elastomer according to claim 1, characterized in that the polyisocyanate described in step (1) is 1.5-naphthalene diisocyanate, and the polyol is polyether or polyester polyol and containing Hydroxy polycarbonate. 3. The method for preparing NDI-based polyurethane microcellular elastomer according to claim 1, characterized in that the -NCO content in the prepolymer in step (1) is ≤ 10.0%. 4. The method for preparing NDI-based polyurethane microcellular elastomer according to claim 2, characterized in that said polyester polyol is a polyester polyol containing side groups. 5. The method for preparing NDI-based polyurethane microcellular elastomer according to claim 4, characterized in that the polyester polyol containing side groups is a polyester polyol containing side methyl groups. 6. The method for preparing NDI-based polyurethane microporous elastomer according to claim 5, characterized in that the polyester polyol containing side methyl groups has a molecular weight of 800-3500 and a functionality of 2-3 Side methyl polyester polyol. 7. The method for preparing NDI-based polyurethane microcellular elastomer according to claim 1, characterized in that the chain extender component in step (2) includes catalyst, blowing agent and surfactant component A mixture of the same polyester components as the polyester polyol described in step (1). 8. The preparation method of NDI-based polyurethane microcellular elastomer according to claim 1, characterized in that the mixing ratio in step (2) is 100:8-15. 9. The method for preparing NDI-based polyurethane microporous elastomer according to claim 7, characterized in that the catalyst is a tertiary amine catalyst. 10. The method for preparing NDI-based polyurethane microcellular elastomer according to claim 7, characterized in that said surfactant is a non-ionic surfactant. 11. The method for preparing NDI-based polyurethane microcellular elastomer according to claim 7, characterized in that the foaming agent is water. 12. The method for preparing NDI-based polyurethane microcellular elastomer according to any one of claims 1-9, characterized in that a low-pressure foaming machine is used to measure and mix the prepolymer and chain extender components.

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