A process for the preparation of a polyurethane microcellular elastomer

Abstract

The application relates to the material field and relates to a preparation method of a polyurethane microporous elastomer, which comprises the following steps: step 1, heating a mold to 90 DEG C + / - 5 DEG C, and injecting a component a into the mold; step 2, keeping the mold temperature, and injecting a component b into the mold; step 3, rotating the mold to mix the component a and the component b in the mold, heating the mold to 110 DEG C + / - 5 DEG C, and continuously rotating the mold to make the mixture react and solidify to form a product, and the product is aged and demolded to obtain the polyurethane microporous elastomer. The application can guarantee the performance of the finally obtained polyurethane microporous elastomer.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to polyurethane microporous materials. Background Technology

[0002] Patent No. 2016103517108, Publication No. 106008872A, entitled "A Polyurethane Microporous Elastomer and Its Preparation and Application," discloses a method for preparing a polyurethane microporous elastomer, as follows:

[0003] Step 1: React diisocyanate and polyhydroxy compound to obtain a prepolymer containing carbamate and isocyanate-terminated, add polymerization inhibitor in proportion as component a (to be stored at 90°C);

[0004] Step 2: Mix the polyhydroxy compound, foaming agent, chain extender, crosslinking agent, additives and catalyst in proportion to obtain component b (which needs to be stored at 60°C);

[0005] Step 3: Mix component A and component B, stir, pour into a mold (mold temperature 90℃-110°C), seal the mold to allow the mixture to react and solidify, remove and cure (heat at 110℃ for 12 hours) to obtain polyurethane microporous elastomer.

[0006] In actual production, it was found that: 1. With increasing storage time, the performance of components A and B gradually declines, resulting in a significant decrease in the final performance of the polyurethane microporous elastomer. 2. Inhomogeneous mixing of components A and B leads to a significant decrease in the performance of the polyurethane microporous elastomer. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a polyurethane microporous elastomer to solve at least one of the above-mentioned technical problems.

[0008] The technical problem solved by this invention can be achieved by the following technical solutions:

[0009] A method for preparing a polyurethane microporous elastomer, characterized by comprising the following steps:

[0010] Step 1: Heat the mold to 90℃±5℃ and inject component a into the mold. The component a is a prepolymer containing urethane and isocyanate-terminated by reacting diisocyanate and polyhydroxy compound. Add polymerization inhibitors in proportion as component a.

[0011] Step 2: Maintain the mold temperature and inject component b into the mold, wherein the polyhydroxy compound, foaming agent, chain extender, crosslinking agent, additives and catalyst are mixed in proportion to obtain component b;

[0012] Step 3: Rotate the mold to mix components a and b inside the mold, heat the mold to 110°C±5°C, and continue to rotate the mold to allow the mixture to react, solidify, and mature. After demolding, polyurethane microporous elastomer is obtained.

[0013] First, this invention directly adds components A and B into the mold, eliminating the need for corresponding storage devices and environments, thus reducing production difficulty. More importantly, it effectively shortens the storage time of the components, thereby ensuring the performance of the final polyurethane microporous elastomer. Second, this invention mixes components A and B inside the mold, rather than outside, effectively maintaining the mixing temperature and avoiding the problem of low mixing efficiency caused by temperature drops during mixing. Crucially, mixing inside the mold eliminates the time required to add the mixture to the mold, further ensuring the performance of the final polyurethane microporous elastomer. Third, during the mixing, curing, and maturation processes, the mold rotates continuously. Under centrifugal force, the outer layer ions are densely arranged, forming a smoother outer surface, while the inner layer ions have stronger penetrability, forming a richer microporous morphology.

[0014] Preferably, the mold includes a tubular inner wall and a tubular outer wall, the top of the inner wall and the outer wall are closed by a top, and the bottom of the inner wall and the outer wall are closed by a bottom, thereby forming a cylindrical cavity between the inner wall, the outer wall, the top, and the bottom, with the outer wall serving as the outer wall of the cavity.

[0015] Further preferably, the outer wall of the mold cavity has a smooth surface.

[0016] Further preferably, the inner sidewall has an injection hole, through which components a and b are injected.

[0017] In a further preferred embodiment, the inner sidewall has an opening at the top and is closed at the bottom, thereby connecting the inner cavity enclosed by the inner sidewall with the injection hole. Component b is directly injected into the inner cavity through the opening of the inner sidewall, and then component b is injected into the cavity between the inner and outer sidewalls through the injection hole.

[0018] Further preferably, a heating device is provided on the periphery of the outer wall, and the heating device is cylindrical.

[0019] Preferably, the mold rotates about its central axis, which is located in the horizontal direction.

[0020] Further optimization involves injecting component b into the mold while rotating the mold in step 2.

[0021] Further optimization involves rotating the mold in step 2 and between curing stages in step 3, first clockwise and then counterclockwise.

[0022] Further optimization involves the following step: in step 3, during the curing stage, the mold rotates intermittently, that is, it rotates for a few minutes and then stops rotating. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the apparatus for preparing polyurethane microporous elastomers.

[0024] Figure 2 A schematic diagram of the mold structure for preparing polyurethane microporous elastomer;

[0025] Figure 3 A schematic diagram of the exploded structure of the mold for preparing polyurethane microporous elastomer;

[0026] Figure 4 A schematic cross-sectional view of the mold used to prepare polyurethane microporous elastomer;

[0027] Figure 5 This is a schematic diagram of the edge structure of the sub-mold and the master mold in the mold for preparing polyurethane microporous elastomers. Detailed Implementation

[0028] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 A method for preparing a polyurethane microporous elastomer includes the following steps:

[0029] Step 1: Heat mold 1 to 90℃±5℃, and inject component a into mold 1. Component a is a prepolymer containing urethane and isocyanate-terminated by reacting diisocyanate and a polyhydroxy compound. An inhibitor is added in a specific ratio as component a. The diisocyanate, polyhydroxy compound, inhibitor, and their proportions are preferably the same as those in patent number 2016103517108, publication number 106008872A, entitled "A Polyurethane Microporous Elastomer and Its Preparation and Application".

[0030] Yes, mold 1 includes a tubular inner wall 2 and a tubular outer wall 3. The top 4 of the inner wall 2 and the outer wall 3 are closed by the top 4, and the bottom 5 of the inner wall 2 and the outer wall 3 are closed by the bottom 5, thus forming a cylindrical cavity between the inner wall 2, the outer wall 3, the top 4, and the bottom 5, with the outer wall 3 serving as the outer wall of the cavity and the inner wall 2 serving as the inner wall of the cavity. This invention optimizes the structure of mold 1, allowing rotation of mold 1 and making the rotation of mold 1 more stable. The side of bottom 5 away from top 4 and the side of top 4 away from bottom 5 can both have outward protrusions or inward recesses, thereby connecting external support components to support mold 1, or connecting external driving components to drive mold 1 to rotate. Mold 1 is divided into two parts with the plane containing the central axis of mold 1 as the dividing plane, one as a sub-mold 6 and the other as a mother mold 7. This facilitates the demolding of polyurethane microporous elastomer. A flange is provided at the joint between the male mold 6 and the female mold 7 to ensure a tighter connection and prevent material from being squeezed out. A support strip 8 can be provided outside the flange, resting against it to increase the support strength. Preferably, an annular protrusion 9 protruding towards the central axis of the mold 1 is provided on the outer wall of the cavity, with the centerline of the annular protrusion 9 coinciding with the central axis of the mold 1. The annular protrusion 9 provides an annular groove on the outer wall 3 of the final polyurethane microporous elastomer, which can be used as an upper support component for automotive shock absorbers.

[0031] Step 2: Maintain the temperature of mold 1 and inject component b into mold 1. Component b is obtained by mixing the polyhydroxy compound, foaming agent, chain extender, crosslinking agent, additives, and catalyst in a specific ratio. The polyhydroxy compound, foaming agent, chain extender, crosslinking agent, additives, and catalyst, as well as their proportions, are preferably the same as those in the patent with patent number 2016103517108, publication number 106008872A, entitled "A Polyurethane Microporous Elastomer and Its Preparation and Application".

[0032] Yes, a heating device 10 is provided outside the mold 1, thereby changing the temperature of the mold 1 using the heating device 10. Preferably, the heating device 10 is cylindrical and surrounds the mold 1. The present invention optimizes the position and structure of the heating device 10. On the one hand, the heating device 10 is close to the object being heated, thereby shortening the heat exchange path, resulting in fast heating speed and high thermal energy utilization. On the other hand, the heating device 10 is wrapped around the object being heated, which plays a role in heat preservation, making the mold 1 dissipate heat slowly, have high thermal stability, and low power consumption of the heating device 10.

[0033] Preferably, an injection hole 11 is provided on the inner sidewall 2, through which components a and b are injected. This invention places the injection hole 11 on the inner sidewall 2, which has the following advantages compared to structures where the injection hole 11 is located on the bottom 5 or top 4: 1. The centrifugal force of the mold 1 can be used to move components a and b away from the injection hole 11, thus eliminating the need for a dedicated structure to seal the injection hole 11. 2. During the reaction process in step 3, carbon dioxide is continuously released, and the unsealed injection hole 11 also functions as an vent during the reaction. 3. Being away from the outer sidewall 3, which has a higher temperature, prevents the components of component b, which have relatively low storage conditions, from being damaged during injection. The central axis of the injection hole 11 is preferably at an angle to the central axis of the mold 1, the angle being acute or obtuse, but not a right angle. This tilts the injection hole 11, changing the direction of movement of component b and further improving the degree of material mixing. Yes, the inner wall 2 has an opening at the top 4 and is closed at the bottom 5, so that the inner cavity enclosed by the inner wall 2 is connected to the injection hole 11. Component b is injected directly into the inner cavity through the opening of the inner wall 2, and then component b is injected into the cavity between the inner wall 2 and the outer wall 3 through the injection hole 11.

[0034] Preferably, component b is injected into the mold 1 while the mold 1 is being rotated. This utilizes the centrifugal force of the mold 1 to accelerate the mixing efficiency of components a and b and improve the dispersion uniformity of component b.

[0035] Step 3: Rotate mold 1 to mix component a and component b within mold 1. Heat mold 1 to 110℃±5℃ and continue rotating mold 1 to allow the mixture to react, solidify, and mature. After demolding, a polyurethane microporous elastomer is obtained. The preferred addition ratio of component a and component b is the same as that in patent number 2016103517108, publication number 106008872A, entitled "A Polyurethane Microporous Elastomer and Its Preparation and Application." Preferably, the outer wall of the cavity of mold 1 has a smooth surface, resulting in a smooth outer surface of the molded polyurethane microporous elastomer. Alternatively, a surfactant can be coated on the cavity wall of mold 1 to further smooth the outer surface of the molded polyurethane microporous elastomer.

[0036] In steps 1, 2, and 3, the rotation of mold 1 is preferably around its central axis, which is horizontal. Placing mold 1 horizontally, compared to vertical placement, avoids the problems of material stratification and uneven mixing of components A and B due to gravity. In step 2, the rotation direction of mold 1, and in step 3 between curing stages, is preferably clockwise followed by counter-clockwise rotation, thus altering the movement direction of component B. In step 3, during the curing stage, mold 1 can rotate intermittently, rotating for a few minutes, stopping, and then rotating for a few more minutes. After curing, continued rotation will not change the mixing of components A and B, but it can make the mixture more evenly heated, thereby shortening the curing time.

[0037] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a polyurethane microporous elastomer, characterized in that, Includes the following steps: Step 1: Heat the mold to 90°C±5°C and inject component a into the mold. The component a is a prepolymer containing urethane and isocyanate-terminated by reacting diisocyanate and polyhydroxy compound. Add a polymerization inhibitor in proportion as component a. Step 2: Maintain the mold temperature and inject component b into the mold. Component b is a mixture of polyhydroxy compound, foaming agent, chain extender, crosslinking agent, additives, and catalyst in a specific ratio. Component b is injected into the mold while rotating it. Step 3: Rotate the mold to mix component a and component b inside the mold, heat the mold to 110°C±5°C, and continue to rotate the mold to allow the mixture to react, solidify, and mature. After demolding, polyurethane microporous elastomer is obtained. The mold includes a tubular inner wall and a tubular outer wall. The tops of the inner wall and the outer wall are closed by a top, and the bottoms of the inner wall and the outer wall are closed by a bottom, thereby forming a cylindrical cavity between the inner wall, the outer wall, the top, and the bottom, with the outer wall serving as the outer wall of the cavity. An injection hole is provided on the inner sidewall, through which components a and b are injected. In step 2, the mold rotates clockwise first, and then counterclockwise, during the curing process in step 3.

2. The method for preparing a polyurethane microporous elastomer according to claim 1, characterized in that, The outer wall of the mold cavity has a smooth surface.

3. The method for preparing a polyurethane microporous elastomer according to claim 1, characterized in that, The inner wall has an opening at the top and is closed at the bottom, so that the inner cavity enclosed by the inner wall is connected to the injection hole. Component b is injected directly into the inner cavity through the opening of the inner wall, and then component b is injected into the cavity between the inner wall and the outer wall through the injection hole.

4. The method for preparing a polyurethane microporous elastomer according to claim 1, characterized in that, A heating device is provided around the outer perimeter of the outer wall, and the heating device is cylindrical.

5. The method for preparing a polyurethane microporous elastomer according to claim 1, characterized in that, The mold rotates about its central axis, which is located in the horizontal direction.

6. The method for preparing a polyurethane microporous elastomer according to claim 1, characterized in that, In step 3, during the curing stage, the mold rotates intermittently, that is, it rotates for a few minutes and then stops rotating.

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