CN115232350B - Method for preparing low-post-shrinkage elastomer foam - Google Patents
Method for preparing low-post-shrinkage elastomer foam Download PDFInfo
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- CN115232350B CN115232350B CN202210349003.0A CN202210349003A CN115232350B CN 115232350 B CN115232350 B CN 115232350B CN 202210349003 A CN202210349003 A CN 202210349003A CN 115232350 B CN115232350 B CN 115232350B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/04—Homopolymers or copolymers of ethene
- C08J2323/08—Copolymers of ethene
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Abstract
The present invention relates to a process for preparing a low post-shrinkage elastomeric foam comprising the steps of: step 1: crosslinking the elastomer to introduce a crosslinked structure; step 2: placing the elastomer in a closed container and heating to a foaming temperature; step 3: injecting high-pressure gas into the closed container for saturation, wherein the saturation pressure is less than 10MPa; step 4: when the high-pressure gas in the closed container is saturated for a certain time to reach saturation balance, the pressure in the closed container is quickly released; step 5: the elastomer is cooled to obtain an elastomer foam. The method disclosed by the invention has a simple process, can effectively improve the post-shrinkage phenomenon of the elastomer foam in the foaming process, prepares the low-density elastomer foam, and simultaneously can control the saturation pressure in a lower range so as to reduce the requirement on equipment.
Description
Technical Field
The invention designs a method for preparing low-post-shrinkage elastomer foam, and particularly relates to a method for preparing a low-density foam material with high dimensional stability by injecting mixed high-pressure gas and saturating the mixed high-pressure gas in a high-temperature environment.
Background
Physical foaming technology is an advanced processing technology using high-pressure fluid/supercritical fluid CO2 or N2 as a foaming agent. Compared with chemical foaming, the foam has the advantages of green environment protection, no toxicity, no harm and no residue. The foaming sample prepared by chemical foaming can realize the same performance or even obtain better performance by utilizing physical foaming under the regulation and control of the process. The microcellular elastomer foam prepared by physical foaming technology using an elastomer as a raw material has buffering and damping properties and excellent resilience properties. Of these, the most representative is the Boost series running shoes developed by the germany Adidas and BASF company, and TPU expanded beads are prepared by using a physical expansion technology and applied to running shoe midbody, and have excellent rebound damping performance and better wear resistance. The product is popular, which accelerates the popularization of the technology of physical foaming in the field of elastomer foam.
CO2 has the characteristics of no toxicity, no harm and no residue, has higher diffusion coefficient, and can prepare foam with high foaming multiplying power under lower saturation pressure. The elastomeric foam obtained after pressure relief foaming is filled with a large amount of CO2, the rate of out-diffusion of CO2 in the cells being two orders of magnitude higher than the rate of out-diffusion of air into the cells, which creates a larger pressure differential inside the elastomeric foam. The elastomer has good elasticity at room temperature and lower corresponding modulus, so that a sample subjected to pressure relief can obviously shrink under the action of internal and external pressure difference in a short time, the foaming multiplying power is reduced, the stability of the material is poor, the rejection rate is high, and meanwhile, the preparation of the high-foaming-ratio elastomer foam is more difficult, so that the service performance and the application field of the elastomer foam are greatly limited.
In the Chinese patent with the publication number of CN104262940A, a color TPU foaming material, a preparation method and application, the technical scheme is disclosed that TPU foaming material which is not shrunk yet is put into high-pressure air or high-pressure nitrogen with the pressure of 0.15-0.5 MPa, so that the external high-pressure air or nitrogen is replaced by high-pressure fluid in the color TPU foaming particles, and shrinkage marks of the TPU foaming material are avoided.
In chinese patent publication No. CN111376503a, "a method for accelerating volume recovery of an elastomer foam material", it is disclosed that an elastomer foam material after shrinkage is saturated by injecting high-pressure nitrogen, and then a sample is placed in an environment with softening temperature of ±20deg.C for recovery, so that the elastomer foam material in a shrunk state is quickly recovered in a short time.
In Chinese patent publication No. CN109293973A, "a polymer micro-foaming material and a forming process thereof", different solubilities of N2 and CO2 in TPU and nucleation capability in the foaming process are utilized, and unstable thermodynamic conditions are manufactured by rapid heating foaming, so that TPU foaming beads with a bimodal cell structure and density of 0.15-0.28 g/cm < 3 >.
The solubility and diffusion rate of high pressure nitrogen in the polymer are low, so that nitrogen as a physical blowing agent often requires extremely high nitrogen pressure, which is a high pressure requirement on equipment, and the diffusion rate is slow and time consuming, but the stability of the foamed sample is superior to that of an elastomer foam prepared with CO 2.
Thus, there is a need for a low cost and efficient manufacturing process to produce stable high performance elastomeric foams.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: a low cost and efficient manufacturing process has been developed to produce stable high performance elastomeric foams.
In order to solve the technical problems, the invention adopts the following technical scheme:
the present invention relates to a process for preparing a low post-shrinkage elastomeric foam comprising the steps of:
step 1: crosslinking the elastomer to introduce a crosslinked structure;
step 2: placing the elastomer subjected to crosslinking treatment in a closed container and heating to a foaming temperature, wherein the foaming temperature is higher than the melting point of the elastomer;
step 3: injecting high-pressure gas into a closed container for saturation, wherein the high-pressure gas comprises a first gas and a second gas, the first gas is carbon dioxide, the second gas is air, nitrogen or mixed gas of air and nitrogen, and the saturation pressure is less than 10MPa;
step 4: when the high-pressure gas in the closed container is saturated for a certain time to reach saturation balance, the pressure in the closed container is quickly released;
step 5: the elastomer is cooled to obtain an elastomer foam.
Further, in the above method for preparing a low post-shrinkage elastomer foam, the elastomer is one or a mixture of several of a modified or non-modified polyolefin elastomer, a styrenic thermoplastic elastomer, or a styrenic thermoplastic elastomer.
Further, in the above method for producing a low post-shrinkage elastomer foam, in the step 3, the saturation pressure is 6 to 10MPa.
Further, in the above method for producing a low post-shrinkage elastomer foam, in the step 3, the saturation pressure is 8 to 10MPa.
Further, in the above method for preparing a low post-shrinkage elastomer foam, in the step 2, the foaming temperature is tm+10 to tm+100 ℃ of the elastomer.
Further, in the above method for preparing a low post-shrinkage elastomer foam, in the step 1, the crosslinking is chemical crosslinking by adding peroxide or sulfur to the elastomer.
Further, in the above method for producing a low post-shrinkage elastomer foam, the peroxide is selected from dicumyl peroxide, bis (t-butylperoxyisopropyl) benzene, 1-bis (t-butylperoxy) -3, 5-trimethylcyclohexane or t-butylcumyl peroxide.
Further, in the above method for preparing a low post-shrinkage elastomer foam, the step 4 specifically comprises: when the high-pressure gas in the closed container is saturated for 30-60min, after the saturation balance is reached, the pressure in the closed container is quickly released, and the pressure releasing speed is 100-600 MPa/s.
Further, in the above method for producing a low post-shrinkage elastomer foam, the rate of the release pressure is 300MPa/s.
Further, in the above method for producing a low post-shrinkage elastomer foam, the ratio of the first gas to the second gas is (0.2 to 2) to 1.
Further, the present invention also relates to a process for preparing a low post-shrinkage elastomeric foam, said process employing a foaming device comprising:
a base;
the foaming box body is connected to the base, and an opening is formed in the upper portion of the foaming box body;
the cover body is positioned above the opening of the foaming box body;
the first lifting driving device is connected to the cover body and is used for driving the cover body to move up and down;
the support plate is arranged in the foaming box body in a lifting manner, and a heating piece is arranged in the support plate and used for heating the surface of the heating support plate;
the second lifting driving device is connected to the lower part of the foaming box body and is connected to the lower part of the supporting plate and used for driving the supporting plate to move up and down;
the air inlet pipe is connected to one side of the foaming box body and is connected with a valve;
the exhaust pipe is connected to one side of the foaming box body and is connected with a valve;
the air outlet of the cooling fan is arranged at one side of the upper edge of the foaming box body;
the method comprises the following steps:
step 1: crosslinking the elastomer to introduce a crosslinked structure to obtain a crosslinked elastomer sheet;
step 2: placing the elastomer sheet after the crosslinking treatment on a supporting plate in a foaming box body, controlling a first lifting driving device to drive a cover body to be in sealing connection with the foaming box body, controlling a second lifting driving device to drive the supporting plate to enable the upper surface of a bottom plate of the foaming box body at the lower part of the supporting plate to be in sealing connection, enabling a closed container to be formed among the supporting plate, the foaming box body and the cover body, controlling a heating piece to heat the supporting plate, and enabling the elastomer sheet on the supporting plate to be heated to a foaming temperature which is higher than the melting point of an elastomer;
step 3: injecting high-pressure gas into the closed container through an air inlet pipe for saturation, wherein the high-pressure gas comprises first gas and second gas, the first gas is carbon dioxide, the second gas is air, nitrogen or mixed gas of air and nitrogen, and the saturation pressure is less than 10MPa;
step 4: when the high-pressure gas in the closed container is saturated for a certain time to reach saturation balance, the valve of the exhaust pipe is opened to quickly release the pressure in the closed container;
step 5: when the pressure in the airtight container tends to normal pressure, the first lifting driving device is controlled to drive the cover body to move upwards and separate from the foaming box body, the second lifting driving device is controlled to drive the supporting plate to move upwards to the upper edge of the foaming box body, and the cooling fan is controlled to cool the elastomer, so that the elastomer is cooled to room temperature quickly, and the elastomer foam is obtained.
The invention has the beneficial effects that: the invention prepares the low-post-shrinkage low-density foam by introducing a cross-linking structure into the elastomer and combining the synergistic effect of a foaming process. The cross-linking structure is introduced into the elastomer, so that the elastomer can be saturated at high temperature, the crystal is completely melted at high temperature, the movement capacity of a molecular chain is high, the elastomer can be rapidly expanded at the moment of foaming, and can be recrystallized in situ when rapidly cooled after foaming, thereby playing a role of a physical cross-linking point and relieving the strong internal stress generated in the foaming process; by CO at high pressure 2 Introducing low diffusion rate N therein 2 And/or compressing air to reduce the rate of out-diffusion of gas in the cells of the foamed sample, thereby reducing the pressure differential between the inside and outside and slowing down the shrinkage of the elastomeric foam. By using the method, high foaming multiplying power can be realized under low saturation pressure, and a stable foaming sample can be obtained.
The elastomer foam is placed in a room temperature environment after foaming, the elastomer is rapidly crystallized in situ at room temperature, gas exchange occurs inside and outside the foam cells, and carbon dioxide in the foam cells escapes outwards. But the inside nitrogen gas/air escape rate of bubble is low and the pressure is high, can maintain the inside sufficient atmospheric pressure of cell at gas exchange's in-process to play the effect of supporting the cell structure, can effectually avoid the unstability of elastomer cell after the foaming, thereby can maintain the higher foaming multiplying power of elastomer foam.
Drawings
Fig. 1 is a schematic structural view of a foaming device according to an embodiment of the present invention.
Detailed Description
In order to describe the technical contents, the achieved objects and effects of the present invention in detail, the following description is made with reference to the embodiments and the accompanying drawings.
Example 1
Preparation of crosslinked EVA foaming material
(1) EVA (Tm: 70 ℃) to which 0.4kg of BIPB crosslinking agent was added was crosslinked under hot press by a vulcanizing machine to obtain a crosslinked EVA sheet having a thickness of 3 mm.
(2) And placing the EVA sheet into a sealed container, heating the sealed container to the foaming temperature of 120 ℃.
(3) Opening the valve to discharge CO at high pressure 2 Injecting into a sealed container to 4MPa, and adding high pressure N 2 Injecting the mixture into a sealed container to 10MPa through a booster pump, closing a valve, and maintaining the pressure for 30min.
(4) And opening a pressure release valve to quickly release pressure, quickly taking out the sample, and cooling the sample under air to obtain a foaming sample.
The density of the sample obtained after pressure relief was 0.1g/cm 3 The density measured after 24 hours was 0.11g/cm 3 . The density was not significantly changed
Example 2
Preparation of crosslinked EVA foaming material
Example 1 step (3), high pressure CO 2 Injecting into a closed container to 7MPa, and adding high pressure N 2 Injecting into a closed container to 10Mpa by a booster pump, closing a valve, and maintaining the pressure for 30min. The other steps were the same as in example 1.
The density of the sample obtained after pressure relief was 0.08g/cm 3 The density measured after 24 hours was 0.12g/cm 3 。
Example 3 preparation of Low Cross-Linked EVA foam
(1) EVA (Tm: 70 ℃) to which 0.4 part of BIPB crosslinking agent was added was crosslinked under hot press by a vulcanizing machine to obtain a crosslinked EVA sheet having a thickness of 3 mm.
(2) And placing the EVA sheet into a sealed container, heating the sealed container to the foaming temperature of 150 ℃.
(3) Opening the valve to discharge CO at high pressure 2 Injecting into a sealed container to 4MPa, and adding high pressure N 2 Injecting the mixture into a sealed container to 10MPa through a booster pump, closing a valve, and maintaining the pressure for 30min.
(4) And opening a pressure release valve to quickly release pressure, quickly taking out the sample, and cooling the sample under air to obtain a foaming sample.
Is obtained after pressure reliefThe density of the obtained sample was 0.08g/cm 3 The density measured after 24 hours was 0.09g/cm 3 . No significant change in density occurred.
Example 4
Preparation of crosslinked POE foam material
(1) 0.2 part of BIPB crosslinker was added to POE (Tm 70 ℃ C.), and crosslinked under hot press by a vulcanizing machine to obtain a crosslinked POE sheet having a thickness of 5 mm.
(2) The POE sheet is placed in a sealed container, the temperature of the sealed container is raised, and the temperature is heated to 170 ℃.
(3) Opening the valve to discharge CO at high pressure 2 Injecting into a sealed container to 8MPa, and adding high pressure N 2 Injecting the mixture into a sealed container to 2MPa through a booster pump, closing a valve, and maintaining the pressure for 30min.
(4) And opening a pressure release valve to quickly release pressure, quickly taking out the sample, and cooling the sample under air to obtain a foaming sample.
The density of the sample obtained after pressure relief was 0.05g/cm 3 After 24 hours of standing, the density was found to be 0.07g/cm 3 。
Example 5
Referring to fig. 1, the present invention relates to a foaming device of an elastomer, comprising:
a base 1;
a foaming box body 2, wherein the foaming box body 2 is connected with the base 1, and an opening 21 is arranged at the upper part of the foaming box body 2;
a cover 3, wherein the cover 3 is positioned above an opening 21 of the foaming box 2;
the first lifting driving device 4 is connected to the cover body 3, and the first lifting driving device 4 is used for driving the cover body 3 to move up and down;
the support plate 5 is arranged in the foaming box body 2 in a lifting manner, and a heating element is arranged in the support plate 5 and used for heating the surface of the heating support plate 5;
the second lifting driving device 6 is connected to the lower part of the foaming box body 2, and the second lifting driving device 6 is connected to the lower part of the supporting plate 5 and used for driving the supporting plate 5 to move up and down;
the air inlet pipe 7 is connected to one side of the foaming box body 2, and the air inlet pipe 7 is connected with a valve;
an exhaust pipe 8, wherein the exhaust pipe 8 is connected to one side of the foaming box body 2, and a valve is connected to the exhaust pipe 8;
and an air outlet 9 of the cooling fan is arranged at one side of the upper edge of the foaming box body 2.
In the above structure, the cooling fan is in the prior art, the specific structure is not repeated, and the heating element in the supporting plate 5 can be an electric stove wire or other devices capable of realizing heating and heat conduction.
In the above structure, through the structure of the foaming box body 2, the cover body 3, the first lifting driving device 4, the supporting plate 5, the second lifting driving device 6, the air inlet pipe 7, the air outlet pipe 8 and the cooling fan, the supporting plate 5 is used for supporting the elastomer to be foamed, the cover body 3 and the sealing cover of the foaming box body 2 can be closed or separated through the first lifting driving device 4, the lifting or descending of the supporting plate 5 can be realized through the second lifting driving device 6, the elastomer to be foamed is convenient to take and place, when the supporting plate 5 descends to the bottom, the lower edge of the supporting plate 5 is used for sealing and matching with the bottom of the foaming box body 2, the cover body 3 and the foaming box body 2 form a closed container, high-pressure foaming gas is fed into the closed container through the air inlet pipe 7 for saturation, after saturation reaches saturation balance for a certain time, the closed container can be quickly released through the air outlet pipe 8, the cover body 3 and the foaming box body 2 can be driven to be separated through the first lifting driving device 4, the supporting plate 5 is lifted to the upper part of the foaming box body 2 through the second lifting driving device 6, and the cooling fan on the side part is used for realizing quick cooling, the required of the elastomer to be foamed, the invention has the advantages of high-efficient and stable foaming density, and the invention relates to the low-density elastomer.
As one embodiment, a first sealing strip 10 is arranged at the edge of the supporting plate 5, and a second sealing strip 11 in limit fit with the first sealing strip 10 is arranged at the bottom of the foaming box body 2;
the bottom of the foaming box body 2 is provided with a through hole 22, and the second lifting driving device 6 is connected with the lower part of the supporting plate 5 through the through hole 22.
In the above structure, the through hole 22 at the bottom of the foaming box body 2 is used for avoiding the second lifting driving device 6, so that the second lifting driving device 6 can be connected with the supporting plate 5 in the foaming box body 2 through the through hole 22, when the second lifting driving device 6 drives the supporting plate 5 to descend to the bottom of the foaming box body 2, the first sealing strip 10 and the second sealing strip 11 are just in limit fit, the two sealing strips can be designed to be mutually matched, for example, the structures of the raised strips and the grooves, and the supporting plate 5 and the bottom of the foaming box body 2 form a closed container by utilizing the first sealing strip 10 and the second sealing strip 11.
As one embodiment, the second lifting driving device 6 includes a connecting seat 61, a screw rod 62, a first guide rail 63, a first nut 64, a first sliding seat 65, a second nut 66, a second sliding seat 67, a cross link lifter 68, a second guide rail 69, a third sliding seat 610, and a fourth sliding seat 611;
the connecting seat 61 is connected to the lower part of the foaming box body 2;
the screw rod 62 is horizontally and rotatably connected to the connecting seat 61, the screw rod 62 is provided with a first thread section and a second thread section which are bilaterally symmetrical, the first nut 64 is in matched connection with the first thread section, and the second nut 66 is in matched connection with the second thread section; the first sliding seat 65 is connected to the first nut 64, the second sliding seat 67 is connected to the second nut 66, the first guide rail 63 is connected to the connecting seat 61, the first guide rail 63 is parallel to the screw rod 62, the first sliding seat 65 is connected to the first guide rail 63 in a sliding fit manner, and the second sliding seat 67 is connected to the second guide rail 69 in a sliding fit manner;
two legs at the lower end of the cross-link lifter 68 are pivotally connected to the first nut 64 and the second nut 66, respectively;
the second guide rail 69 is connected to the lower portion of the support plate 5, the third sliding seat 610 is connected to the second guide rail 69 in a sliding fit manner, the fourth sliding seat 611 is connected to the second guide rail 69 in a sliding fit manner, and two legs at the upper end of the cross link lifter 68 are respectively pivoted to the third sliding seat 610 and the fourth sliding seat 611.
In the above structure, by designing the second lifting driving device 6 with a specific structure, the lifting and lowering of the supporting plate 5 is realized by utilizing the cooperation of the components such as the cross connecting rod lifting piece 68, the screw rod 62 and the like, and the lifting and lowering device has the advantages of small occupied space and stable lifting and lowering.
As one embodiment, the air inlet pipe 7 includes a main pipe 71, a first branch pipe 72, and a second branch pipe 73, and the end of the main pipe 71 is connected to one side of the foaming box 2; the first branch pipe 72 and the second branch pipe 73 are respectively connected to the start end of the main pipe 71 through three-way connectors, and the first branch pipe 72, the second branch pipe 73 and the main pipe 71 are respectively provided with valves.
In the above configuration, two different foaming gases can be supplied into the foaming box 2, for example, CO2 or N2 is supplied into the foaming box 2 sequentially or simultaneously.
As one embodiment, a pressure measuring device 14 is connected to one side of the foaming box, and the pressure measuring device 14 is used for measuring the air pressure in the foaming box 2.
As one embodiment, the device further comprises a temperature control device 15, the temperature control device 15 is disposed at the bottom of the foaming box 2, the temperature control device 15 is electrically connected with the heating element, the temperature control device 15 can be connected with the connecting seat 61, and the electric wire can be connected with the bottom of the supporting plate 5 through the through hole 22 at the lower part of the foaming box 2.
As one embodiment, the edge of the cover body 3 is provided with a third sealing strip 12, and the upper edge of the foaming box body 2 is provided with a fourth sealing strip 13 matched with the third sealing strip 12;
in the above structure, the structures of the third sealing strip 12 and the fourth sealing strip 13 can refer to the structures of the first sealing strip 10 and the second sealing strip 11, when the cover body 3 and the foaming box body 2 are covered, the sealing fit of the cover body 3 and the foaming box body 2 can be realized through the three sealing strips and the fourth sealing strip 13, and under the sealing action of the first sealing strip 10, the second sealing strip 11, the third sealing strip 12 and the fourth sealing strip 13, the cover body 3, the foaming box body 2 and the supporting plate 5 form a closed space, so that the space has very high sealing and pressure resistance.
As one embodiment, the first lifting driving device 4 is a driving cylinder, the driving cylinder is a cylinder or a hydraulic cylinder, the cylinder body of the driving cylinder is vertically and downwardly connected to the base 1, and the piston rod of the driving cylinder is connected to the cover 3;
the upper portion of the cover body 3 is connected with a limiting shaft 31 in the vertical direction, the base 1 is provided with a shaft sleeve which is in sliding fit with the limiting shaft 31, and when the cover body 3 moves up and down, the limiting shaft 31 can play a role in guiding, so that accurate butt joint between the cover body 3 and the foaming box body 2 is further guaranteed.
The above foaming device for use in a process for preparing a low post-shrinkage elastomeric foam comprising the steps of:
step 1: crosslinking the elastomer to introduce a crosslinked structure to obtain a crosslinked elastomer sheet;
step 2: placing the elastomer sheet after the crosslinking treatment on a supporting plate in a foaming box body, controlling a first lifting driving device to drive a cover body to be in sealing connection with the foaming box body, controlling a second lifting driving device to drive the supporting plate to enable the upper surface of a bottom plate of the foaming box body at the lower part of the supporting plate to be in sealing connection, enabling a closed container to be formed among the supporting plate, the foaming box body and the cover body, controlling a heating piece to heat the supporting plate, and enabling the elastomer sheet on the supporting plate to be heated to a foaming temperature which is higher than the melting point of an elastomer;
step 3: injecting high-pressure gas into the closed container through an air inlet pipe for saturation, wherein the high-pressure gas comprises first gas and second gas, the first gas is carbon dioxide, the second gas is air, nitrogen or mixed gas of air and nitrogen, and the saturation pressure is less than 10MPa;
step 4: when the high-pressure gas in the closed container is saturated for a certain time to reach saturation balance, the valve of the exhaust pipe is opened to quickly release the pressure in the closed container;
step 5: when the pressure in the airtight container tends to normal pressure, the first lifting driving device is controlled to drive the cover body to move upwards and separate from the foaming box body, the second lifting driving device is controlled to drive the supporting plate to move upwards to the upper edge of the foaming box body, and the cooling fan is controlled to cool the elastomer, so that the elastomer is cooled to room temperature quickly, and the elastomer foam is obtained.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent changes made by the specification and drawings of the present invention, or direct or indirect application in the relevant art, are included in the scope of the present invention.
Claims (9)
1. A method of preparing a low post-shrinkage elastomeric foam, wherein the method employs a foaming device comprising:
a base;
the foaming box body is connected to the base, and an opening is formed in the upper portion of the foaming box body;
the cover body is positioned above the opening of the foaming box body;
the first lifting driving device is connected to the cover body and is used for driving the cover body to move up and down;
the support plate is arranged in the foaming box body in a lifting manner, and a heating piece is arranged in the support plate and used for heating the surface of the heating support plate;
the edge of the supporting plate is provided with a first sealing strip, and the bottom of the foaming box body is provided with a second sealing strip in limit fit with the first sealing strip;
the second lifting driving device is connected to the lower part of the foaming box body and is connected to the lower part of the supporting plate and used for driving the supporting plate to move up and down;
the second lifting driving device comprises a connecting seat, a screw rod, a first guide rail, a first nut, a first sliding seat, a second nut, a second sliding seat, a cross connecting rod lifting piece, a second guide rail, a third sliding seat and a fourth sliding seat;
the connecting seat is connected to the lower part of the foaming box body;
the bottom of the foaming box body is provided with a through hole, and the second lifting driving device is connected with the lower part of the supporting plate through the through hole;
the air inlet pipe is connected to one side of the foaming box body and is connected with a valve;
the exhaust pipe is connected to one side of the foaming box body and is connected with a valve;
the air outlet of the cooling fan is arranged at one side of the upper edge of the foaming box body;
the temperature control device is arranged at the bottom of the foaming box body, the temperature control device is electrically connected with the heating piece, the temperature control device can be connected to the connecting seat, and the electric wire can be connected with the bottom of the supporting plate through a through hole at the lower part of the foaming box body;
the method comprises the following steps:
step 1: crosslinking the elastomer to introduce a crosslinked structure to obtain a crosslinked elastomer sheet;
step 2: placing the elastomer sheet after the crosslinking treatment on a supporting plate in a foaming box body, controlling a first lifting driving device to drive a cover body to be in sealing connection with the foaming box body, controlling a second lifting driving device to drive the supporting plate to enable the upper surface of a bottom plate of the foaming box body at the lower part of the supporting plate to be in sealing connection, enabling a closed container to be formed among the supporting plate, the foaming box body and the cover body, controlling a heating piece to heat the supporting plate, and enabling the elastomer sheet on the supporting plate to be heated to a foaming temperature which is higher than the melting point of an elastomer;
step 3: injecting high-pressure gas into the closed container through an air inlet pipe for saturation, wherein the high-pressure gas comprises first gas and second gas, the first gas is carbon dioxide, the second gas is air, nitrogen or mixed gas of air and nitrogen, and the saturation pressure is less than 10MPa;
step 4: when the high-pressure gas in the closed container is saturated for a certain time to reach saturation balance, the valve of the exhaust pipe is opened to quickly release the pressure in the closed container;
step 5: when the pressure in the airtight container tends to normal pressure, the first lifting driving device is controlled to drive the cover body to move upwards and separate from the foaming box body, the second lifting driving device is controlled to drive the supporting plate to move upwards to the upper edge of the foaming box body, and the cooling fan is controlled to cool the elastomer, so that the elastomer is cooled to room temperature quickly, and the elastomer foam is obtained.
2. The method of preparing a low post-shrinkage elastomeric foam according to claim 1, wherein the elastomer is one or a mixture of several of a modified or non-modified polyolefin elastomer, a styrenic thermoplastic elastomer.
3. The method of preparing a low post-shrinkage elastomeric foam according to claim 1, wherein in step 3, the saturation pressure is 6 to 10MPa.
4. The method of preparing a low post-shrinkage elastomeric foam according to claim 1, wherein in step 2, the foaming temperature is tm+10 to tm+100 ℃ of the elastomer.
5. The method of preparing a low post-shrinkage elastomer foam according to claim 1, wherein in step 1, the crosslinking is chemical crosslinking by adding peroxide or sulfur to the elastomer.
6. The method of preparing a low post-shrinkage elastomeric foam according to claim 5, wherein the peroxide is selected from the group consisting of dicumyl peroxide, bis (t-butylperoxyisopropyl) benzene, 1-bis (t-butylperoxy) -3, 5-trimethylcyclohexane, and t-butylcumyl peroxide.
7. The method for preparing a low post-shrinkage elastomeric foam according to claim 1, wherein said step 4 is specifically: when the high-pressure gas in the closed container is saturated for 30-60min, after the saturation balance is reached, the pressure in the closed container is quickly released, and the pressure releasing speed is 100-600 MPa/s.
8. The method of preparing a low post-shrinkage elastomeric foam according to claim 7, wherein the rate of release pressure is 300MPa/s.
9. The method of preparing a low post-shrinkage elastomeric foam according to claim 1, wherein the ratio of the first gas to the second gas is (0.2-2) to 1.
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