CN113246367B

CN113246367B - Novel foaming adhesive forming process

Info

Publication number: CN113246367B
Application number: CN202110645823.XA
Authority: CN
Inventors: 梁颖颐; 梁冠华
Original assignee: Dongguan Lida Sporting Goods Co ltd
Current assignee: Dongguan Lida Sporting Goods Co Ltd; Shenzhen Jiebubao Sports Technology Co ltd
Priority date: 2021-06-09
Filing date: 2021-06-09
Publication date: 2021-11-02
Anticipated expiration: 2041-06-09
Also published as: CN113246367A

Abstract

The invention discloses a novel foaming glue forming process, which comprises the following steps: s1, preparing a radio frequency foaming mold S2, filling the mold, and closing the mold; s3, preparing materials, namely preparing a foamed collagen material, mixing the foamed collagen material with a polar medium material, and fully stirring to obtain a mixture A; s4, tightly buckling a metal hood in the die equipment to ensure that radio frequency electric waves cannot leak; s5, filling, and enabling the mixture A to enter a product cavity in a vacuum and/or negative pressure mode; s6, adjusting the radio frequency emission parameters of the radio frequency generator; s7, carrying out radio frequency heating, namely, applying the mixture A to a position through a radio frequency generator to rapidly heat, heat up, weld, fuse and form; s8, cooling, namely absorbing the heat of the die in a vacuum and/or negative pressure mode, and opening a hood for air cooling; and S9, opening the die and taking out the product. The novel foaming glue forming process can improve the yield of finished products, reduce heat energy loss, and is more energy-saving and environment-friendly; in addition, the heating and adjusting response speed is high, and the molding effect of the material is ensured.

Description

Novel foaming adhesive forming process

Technical Field

The invention relates to the technical field of foaming adhesive forming, in particular to a novel foaming adhesive forming process.

Background

The foamed rubber product has the characteristics of light weight, good quality, high strength, good buffering and shockproof effects, heat insulation and preservation and the like, and is widely applied to industries such as human body protectors, automobile energy absorption parts, heat preservation, packaging and the like. Common foam rubber materials include expanded polystyrene, expanded polypropylene, expanded polyethylene, and the like.

The foaming glue forming technique that uses in the trade at present mainly is as the heat source with vapor, and vapor will use industrial boiler, and nevertheless the shaping quality of this mode is difficult for observing, has the potential safety hazard, and the boiler that uses needs great factory building area, need use natural gas and coal burning to produce heat energy simultaneously, and the feature of environmental protection is relatively poor, has more calorific loss at the in-process of heat transport, and response speed is slow, and temperature regulation flexibility is poor.

The patent file of retrieval can find that 2018 quan state institute of professor applied for application number 201820314655.X utility model name polymer material foaming device, the radio frequency that its radiofrequency generator produced is leading-in to the die cavity through the waveguide, however the waveguide only has an inlet port, and leading-in radio frequency wave is inhomogeneous in whole die cavity, can't 360 degrees circumference do not have the dead angle ground to all materials foam, the local material can not foam because can't receive the radio frequency wave problem.

The applicant's quanzhou college of academic and vocational study, application number 201810188366.4, the name of the invention is a polymer foaming device and a method for foaming a polymer by adopting the device. However, the electrodes are energized and therefore it is necessary to provide a conductive insulating layer, which will certainly destroy the internal structure of the mold cavity. In practical application, the upper and lower radio frequency electrodes are abraded by repeatedly injecting a material into the die cavity for foaming and vibrating for demoulding, so that the electrode deformation is easily caused, and the product quality is influenced. In addition, the electrodes are electrified, and the foaming material injected into the die cavity is also an electric conductor, so that the electric energy is still guided to the die by the conductive foaming material when foaming is undoubtedly carried out, and therefore, even if a conductive insulating layer is designed, the insulating effect of the die is not really well achieved.

The invention discloses a polymer foaming forming device, which belongs to the field of spring State academy of education, application number 201810187258.5 and discloses a foaming formula and a radio frequency foaming process of a high polymer foaming material. It is also specifically noted that polytetrafluoroethylene (Teflon or PTFE) is used as the mold material, however, polytetrafluoroethylene has poor thermal conductivity and does not substantially increase the temperature of the PTFE mold when the foam in the mold cavity is heated to about 100 degrees. And polytetrafluoroethylene is nonpolar, and the high-frequency electric field of radio frequency wave can not produce the effect of rising the temperature to polytetrafluoroethylene, therefore with the mould of polytetrafluoroethylene (Teflon or PTFE) material, it is difficult to realize the welding quality on product surface, is helpless to the welding fusion quality of expanded polystyrene material. The PTFE molds need to be preheated to solve the problem, and the addition of preheating adds significant complexity to the overall rf process, and is time consuming in addition to the need to add a heat source (e.g., steam, hot oil, hot air, or other hot medium) to heat the PTFE molds.

Disclosure of Invention

The invention aims to provide a novel foaming adhesive forming process to at least solve the problem of poor welding and fusing quality of a foaming adhesive material in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme:

a novel foaming glue forming process comprises the following steps:

s1, preparing a radio frequency foaming mold, wherein the radio frequency foaming mold comprises a radio frequency generator, an upper mold, a lower mold, an upper mold electrode and a lower mold electrode, the upper mold and the lower mold are opposite to each other and can be opened and closed, when the upper mold and the lower mold are closed, a product cavity is formed, the upper mold electrode is installed on the upper mold, the lower mold electrode is installed on the lower mold, the radio frequency generator is electrically connected to the upper mold electrode through an upper mold radio frequency conducting wire and is also electrically connected to the lower mold electrode through a lower mold radio frequency conducting wire, the product cavity is communicated with a foaming glue raw material system through a filling gun, communicated with a vacuum system through a vacuum pipeline and communicated with a compression air system through a forming compression air pipeline, the other end of the compression air system is communicated to the filling gun through a filling compression air pipeline, and the front ends of the upper mold, the lower mold and the filling gun are made of polar non-metallic materials: the PET material added with 25 percent of glass fiber and heat-conducting filler or the nylon material added with 25 percent of glass fiber;

s2, die filling and die assembly;

s3, preparing materials, namely preparing a foamed collagen material, mixing the foamed collagen material with a polar medium material, and fully stirring to obtain a mixture A, wherein the mixing ratio of the polar medium material to the foamed collagen material is 50% -65%;

s4, tightly buckling a metal hood in the die equipment to ensure that radio frequency electric waves cannot leak;

s5, filling, and enabling the mixture A to enter the product cavity 15 in a vacuum and/or negative pressure mode;

s6, adjusting the parameters of the radio frequency generator (1), taking the voltage of a radio frequency power supply as the parameters of the tuning, processing the voltage in sections, boosting the voltage from low to high, applying 2KV voltage in the first stage for 2 seconds; in the second stage, 2.5KV voltage is applied for 10 seconds; the third stage is applied with 3KV voltage for 10 seconds; applying 3.5KV voltage for 10 seconds in the fourth stage; in the fifth stage, 4KV voltage is applied for 6 seconds;

s7, performing radio frequency heating, opening a forming compressed air system, starting the radio frequency heating according to the machine adjusting parameters of the step S6, generating radio frequency waves through a radio frequency generator (1), applying the radio frequency waves to the mixture A, rapidly heating the mixture A to 100-110 ℃, and fusing and integrating the foamed adhesive particles into a whole under the condition; after the radio frequency heating is finished, the forming compressed air is closed;

s8, cooling, absorbing heat of the product and the die in a vacuum and/or negative pressure mode, and opening the hood for air cooling;

and S9, opening the die and taking out the product.

The novel foaming glue forming process provided by the invention has the beneficial effects that:

1. the invention is based on the principle that polar materials can be acted by a radio frequency electric field, the polar materials are selected to manufacture the die, and the radio frequency slightly heats the PET die and the nylon die, which is obviously helpful for the fusion welding and fusing quality of the foamed rubber material.

2. The product cavity is connected with a foaming glue raw material system, a vacuum system and a compressed air system;

a compressed air system: the filling gun is connected to serve as the power of filling, and the foaming rubber is brought into a product cavity. Secondly, connecting a product cavity, inputting pressure of about 1-2 bar to the product cavity in the forming process to enable foaming glue particles to be attached tightly, and thirdly, inputting pressure of about 30-40 bar to the product cavity by the compressed air system after foaming to enable a foaming product to be demoulded.

Foaming glue raw material system: the foaming rubber material is loaded in the tank, and the foaming rubber material is mixed with polar medium material with the weight of 50-65% of that of the foaming rubber material and is continuously stirred in a material tank.

A vacuum system: has two functions. Firstly, vacuum pumping auxiliary filling; secondly, vacuumizing and cooling the mold and the product. When the foaming material is injected into the product cavity, the product cavity can form negative pressure in a vacuumizing mode, and unnecessary air is discharged. In addition, because the foaming material is injected and foamed, the material occupies the space of the whole product cavity, and the vacuumizing also has the function of exhausting gas.

The foaming glue raw material system, the vacuum system and the compressed air system are combined with each other for full-automatic continuous operation, manual intervention is not needed, and the automation degree is high.

3. The invention adopts five stages to gradually increase the voltage, and controls the time and voltage value of each stage: 2KV voltage is applied in the first stage for 2 seconds; in the second stage, 2.5KV voltage is applied for 10 seconds; the third stage is applied with 3KV voltage for 10 seconds; applying 3.5KV voltage for 10 seconds in the fourth stage; the fifth stage applies 4KV voltage for 6 seconds, with the benefits of: the whole foaming process only needs 38 seconds, and the foaming speed is very high. And the gradual pressurizing mode can avoid the explosion of the foaming material caused by excessive instantaneous energy, thereby ensuring the appearance quality of the product.

4. The invention directly acts on the material in a radio frequency heating mode, can promote the foaming glue to be molded from inside to outside, ensures the integral foaming quality of the material, improves the yield of finished products, and effectively reduces the heat energy loss compared with the traditional boiler pipeline heat delivery mode.

5. The die equipment is independent equipment, the occupied area is small, the flexibility is strong, the whole equipment can move in a workshop, the heat energy loss is reduced, and the potential safety hazard is effectively reduced.

6. The invention converts the electric energy into the radio frequency wave, and compared with the traditional forming process which adopts a mode of adopting a boiler and burning natural gas or coal, the invention obviously reduces the pollutant emission, and is more energy-saving and environment-friendly.

7. The invention can flexibly control the power and the radio frequency wavelength by adopting the radio frequency generator so as to realize the function of adjusting the heating effect, has high heating and adjusting response speed, and ensures the forming effect of the material by the cooperation with the polar medium material.

Drawings

FIG. 1 is a schematic structural diagram of a mold for a novel foam molding process of the present invention;

FIG. 2 is a schematic diagram of an upper mold and a lower mold of the novel foam rubber molding process of the present invention.

Fig. 3 is a bottom view of the upper mold electrode of the novel foam rubber molding process of the present invention.

FIG. 4 is a cross-sectional view of an upper mold electrode of the novel foam molding process of the present invention.

FIG. 5 is a process flow diagram of the present invention.

In the figure: 1. the radio frequency generator, 2, go up the mould, 3, the lower mould, 4, go up the mould electrode, 5, the lower mould electrode, 6, the filler rifle, 7, lower mould hoist system, 8, the screw, 9, the vacuum pipe, 10, shaping compressed air pipeline, 11, filler compressed air pipeline, 12, the frame, 13, go up mould radio frequency conduction line, 14, lower mould radio frequency conduction line, 15, product die cavity 16, foaming adhesive raw materials system 17, vacuum system 18, compressed air system 19, first heat conduction filler 20, second heat conduction filler 21, go up aluminum plate 22, lower aluminum plate 23, clearance 24, through-hole 25, mounting groove 26, plasma.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-5, the present invention provides a technical solution: a novel foaming glue forming process is used for foaming forming helmets and comprises the following steps:

s1, preparing a special radio frequency foaming mould.

S2, die filling and die assembly; ensuring compactness of the module.

S3, preparing materials, preparing a foamed collagen material, mixing the foamed collagen material with a polar medium material, and fully stirring to obtain a mixture A. Preferably, the foamed collagen material in step S3 includes, but is not limited to: one or more of expanded polystyrene, expanded polyethylene, and expanded polypropylene, and polar vehicle materials include, but are not limited to: one or more of water, hydrogen peroxide, ethanol and alkali liquor, preferably water is used as a polar medium material for radio frequency heating. Preferably, the mixing weight ratio of the polar medium material to the foamed collagen material is 65: the foam molding quality is better at 100 ℃.

S4, tightly buckling a metal cover in the die equipment to ensure that radio frequency waves cannot leak.

And S5, filling, namely enabling the mixture A to enter the product cavity 15 in a vacuum and/or negative pressure mode, and closing the compressed air and vacuum of the filling after filling.

And S6, adjusting the radio frequency emission parameters of the radio frequency generator 1. The voltage of the power supply of the radio frequency generator is used as a tuning parameter, and after a plurality of tests, the voltage is processed in a segmented manner and is boosted from low to high, so that better foaming forming quality can be obtained.

First stage	Second section	Third stage	Fourth stage	Fifth stage
					2KV
2 sec	2.5KV,10 seconds	3KV,10 seconds	3.5KV,10 seconds	4KV,6 seconds

And S7, heating by radio frequency, generating radio frequency waves by the radio frequency generator 1, applying the radio frequency waves to the mixture A, rapidly heating to raise the temperature, welding, fusing and molding. The specific method comprises the following steps: and opening the forming compressed air, and starting the radio frequency heating according to the parameters of the step S6. Through experiments, the temperature of the foam rubber material can be raised to 100-110 ℃ by the parameters, and the foam rubber particles are welded and integrated into a whole under the condition, so that the purpose of forming is achieved. And after the radio frequency heating is finished, closing the forming compressed air.

And S8, cooling, absorbing the heat of the die in a vacuum and/or negative pressure mode, and opening the hood for air cooling. In this embodiment, the vacuum system 17 is preferably turned on to draw heat away from the product and the mold. And opening the hood, and conveying cold air to strengthen the cooling mold. Then, the compressed air system 18 blows air into the product cavity 15, so that air enters from a gap between the mold and the product, the product is forced to be peeled off from the inner wall surface of the product cavity 15 of the mold, and the effect of air blowing and demolding is achieved.

And S9, opening the die and taking out the product.

In addition, the invention also provides a mould of the novel foaming adhesive forming process, which comprises a radio frequency generator 1, an upper mould 2, a lower mould 3, an upper mould electrode 4, a lower mould electrode 5, a filling gun 6, a lower mould lifting system 7, a screw 8, a vacuum pipeline 9, a compressed air system 18, a machine frame 12, an upper mould radio frequency conducting wire 13, a lower mould radio frequency conducting wire 14 and a product cavity 15.

The working principle of the mould of the novel foaming glue forming process is as follows: the radio frequency generator 1 generates radio frequency, and the radio frequency is transmitted to the upper die electrode 4 and the lower die electrode 5 through radio frequency conducting wires; the positive and negative poles of the upper die electrode 4 and the lower die electrode 5 are always alternated and opposite, so that an alternating electromagnetic field is generated, and the alternating electromagnetic field penetrates through the upper die 2 and the lower die 3, so that polar molecules in the molding material reciprocate at a high speed, and the purpose of heating the material is achieved through friction heat generation.

Specifically, the upper die 2 and the lower die 3 are vertically opposed to each other, and a product cavity 15 for molding a product is formed between the upper die 2 and the lower die 3. The cavity can be various shapes, for example, when manufacturing a helmet, different cavity structures are designed according to the helmet texture and the holes, which is not limited herein. The upper mold 2 and the lower mold 3 can be opened and closed with each other. In the embodiment, the upper die 2 is a fixed die, the lower die 3 is a movable die, and the lower die 3 moves up and down through the lower die lifting system 7, so that the die opening and closing action is completed. During the assembly, can all install the frame with last mould 2 and lower mould 3 in, the support of mould is realized on the one hand to this frame, and on the other hand protection mould prevents that the die opening and shutting from to workman's bodily injury, can also play effects such as dustproof and shelter from.

It should be noted that the upper die 2 and the lower die 3 of the present invention are arranged vertically, and the vertical arrangement can be changed into the horizontal arrangement according to different production requirements, for example, considering factors such as the distribution of spatial positions, and the application effect is still effective.

In this embodiment, the upper die 2 is provided with an upper die electrode 4, and the lower die 3 is provided with a lower die electrode 5. In this embodiment, the upper die electrode 4 and the upper die electrode 5 can be fixedly mounted on the inner side of the machine frame 12 by screws 8, but the fixing and non-fixing methods such as fastening, welding, etc. can be used without being limited to using screws. The upper die electrode 4 and the lower die electrode 5 may be attached to the upper die 2 and the lower die 3, respectively, by screws 8 or other fixing means.

Preferably, the upper and

lower electrodes

4 and 5 are made of a metal conductive material such as aluminum, copper, etc., and an aluminum material is preferably used as the electrode material in view of economy and weight. The electrodes should not have sharp corners, which would result in local over-concentration of energy. In addition, the upper die electrode 4 and the lower die electrode 5 are disk thin bodies, and the density of the plasma 26 on the surfaces of the upper die electrode 4 and the lower die electrode 5 is reduced from the center 41 to the edge 42, so that the energy of the center and the edge is adjustably controlled, the thickest position in the middle of the foaming material and the thinner position of the edge can simultaneously and uniformly absorb the energy, and the foaming quality is improved.

Specifically, as shown in fig. 3 and 4, the plasma mounting structure will be described by taking the upper mold electrode 4 as an example. The upper die electrode 4 comprises an upper aluminum plate 21 and a lower aluminum plate 22, a gap 23 is kept between the upper aluminum plate and the lower aluminum plate, a heat dissipation gap is formed by the gap in the middle, and the electrode also forms a heat sink because the aluminum material has good heat dissipation characteristics. The lower aluminum plate is provided with a corresponding through hole 24 corresponding to each plasma 26, and the upper aluminum plate has a corresponding mounting groove 25, so that the plasma is fixed to the through hole and the mounting groove.

The radio frequency generator 1 is installed on the outer side of the machine frame 12, and the radio frequency generator 1 is electrically connected to the upper die electrode 4 through an upper die radio frequency conducting wire 13 and is also electrically connected to the lower die electrode 5 through a lower die radio frequency conducting wire 14. The radio frequency generator radio frequency power supply is used for generating radio frequency electric power, the output of the radio frequency generator radio frequency power supply is generally sine wave or pulse, the frequency has specifications of 2MHz, 13.56MHz, 27.12MHz, 60MHz and the like, the output power is from dozens of watts to dozens of kilowatts, the output impedance is generally 50 ohms, and the radio frequency with the frequency of 13.35MHz or 27.12MHz is preferably selected as machinery equipment according to the size and the energy requirement of a common foamed rubber piece, and the power is preferably 1 KW-30 KW.

In the above foaming method, step S6 mentions that the polar medium material is gradually foamed by applying different energies in five grades. The incident power and the temperature rise rate show corresponding linear relation, so that the incident power and the temperature rise have important effects on the temperature change. When the foaming and polar medium materials are not changed and only the input power is changed, the higher the power is, the larger the heating and temperature rising amplitude of the materials is. Therefore, a larger input power should be selected as much as possible. However, if the high voltage and high power of 4KV in the fifth section are directly selected, the energy of internal molecules is too concentrated to burn the surface, and the material may crack due to the imbalance between the surface temperature and the deep temperature. Therefore, it is reasonably efficient to employ staged heating. The optimal scheme is as follows: a first section of 2 KV; the second section is 2.5 KV; a third section of 3 KV; the fourth section is 3.5 KV; and the fifth section is 4 KV.

The following is a temperature comparison table of the polar vehicle material at five different voltages: the following two sets of parameters were obtained by varying the heating time without changing the other conditions:

table 1 shows the parameters for a heating time of 2 seconds for each stage.

Table 2 shows the parameters of the five stages of heating time at 2 seconds, 10 seconds and 6 seconds.

Table 1 and table 2 are compared to show that: even if the energy is the same for each grade, if the heating time is insufficient, the foaming temperature cannot be increased to 100-110 ℃. In particular, the inventors have shown in their studies that the temperature distribution of the deep and shallow layers of the foam is not uniform, and the temperature of the deep layer is always lower than that of the shallow layer.

Table 2 the heating time parameter is modified for the purpose of raising the temperature of the foaming material so that the foaming temperature is relatively stable and close to the actual heating operation state temperature. In the fifth stage, the deep layer temperature and the shallow layer temperature are relatively balanced, the foaming rate of the foaming rubber material can reach 99.85 percent, the problems of superficial layer surface burning and deep layer cracking are avoided, and the quality is guaranteed.

Even so, it does not mean that the longer the warming time is, the better the warming time is, and if the warming time of each stage is prolonged to 30 seconds, the foaming time is certainly prolonged, the efficiency is lower, and besides, the electric energy is consumed. Therefore, it is reasonably effective to select parameters of the five-stage heating time of 2 seconds, 10 seconds, and 6 seconds.

The mould of the novel foaming glue forming process further comprises a foaming glue raw material system 16, wherein the foaming glue raw material system 16 is positioned outside the machine frame and communicated to the product cavity 15 through a filling gun 6 and used for injecting a foaming material into the product cavity. For example, holes may be formed in the lower mold such that the holes form a flow path that communicates between the foam rubber raw material system 16 and the product cavity 15. The front end of the filling gun 6 is made of non-metal material and is embedded into the lower die. The filling gun is fixed on the back of the lower die electrode by a bolt. The filling gun 6 is connected with the foaming material through a pipeline.

Preferably, the foam rubber material system 16 is loaded with a foam rubber material. The foamed rubber material is mixed with water in 50-65 wt% and stirred constantly in a material tank.

Conventional foamed-rubber materials include expanded polystyrene (hereinafter abbreviated as EPS), expanded polystyrene and polyethylene copolymer (hereinafter abbreviated as EPO), expanded polypropylene (hereinafter abbreviated as EPP), expanded polyethylene (hereinafter abbreviated as EPE). These materials are not polar materials and typically are heated without the rf electromagnetic waves causing them to react. Therefore, the polar medium is mixed with the foamed collagen material, and the liquid is most suitable. The polar liquids are: water, hydrogen peroxide, ethanol, alkali liquor and the like. Water is preferred as a medium for rf heating in view of economy and safety. According to research, the weight percentage of the water and the foaming glue is 50-65%, and the foaming molding quality is highest.

The mould of the invention is further provided with a vacuum system 17, and the vacuum system 17 is communicated to the product cavity 15 through a vacuum pipeline. The vacuum system 17 is connected to two functions. Firstly, vacuum pumping auxiliary filling; secondly, vacuumizing and cooling the mold and the product. When the foaming material is injected into the product cavity 15, the product cavity 15 can form negative pressure in a vacuum pumping mode to discharge unnecessary air. In addition, since the space of the product cavity 15 is occupied by the foaming material during the injection and foaming, the evacuation also has a function of exhausting gas.

The mould is further provided with a compressed air system 18, and the compressed air system 18 comprises a forming compressed air pipeline 10 and a filler compressed air pipeline 11. One end of the compressed air system 18 is communicated to the product cavity 15 through a molding compressed air pipeline 10, and the other end is communicated to the filling gun 6 through a filling compressed air pipeline 11. The compressed air system 18 has three functions, one is to connect a filling gun as the power of filling and bring the foaming rubber into the product cavity. Secondly, connecting a product cavity, inputting pressure of about 1-2 bar into the product cavity in the forming process to enable foaming glue particles to be attached tightly, and thirdly, inputting pressure of about 30-40 bar into the product cavity 15 by the compressed air system 18 after foaming to enable a foamed product to be demoulded.

The material analysis shows that the mould materials of the upper mould 2 and the lower mould 3 and the front end of the filling gun 6 are non-metal materials, because the conductive materials can obstruct the radio frequency from passing through, the purpose of heating the forming material can not be achieved, the mould can be heated in a centralized manner, even sparks can be generated, the mould is damaged, and therefore the non-metal materials are selected as the mould materials. Considering the working conditions of the die: cold and hot alternation, extrusion, easy collision, and preferably, the material is tough, wear-resistant, temperature-resistant, fatigue-resistant, good in dimensional stability and more economical, such as PET, PTFE, nylon, PC and the like. More preferred are polar materials such as PET plus 25% fiberglass, nylon plus 25% fiberglass.

In the research and development process of the invention, the radio frequency is found to slightly heat the PET mould, which is obviously helpful for the fusion quality of the foamed rubber material. The principle of PET mold heating is mainly due to the fact that the central atom in PET contains lone pair electrons, and the attached electrons have different electronegativities. The polar group of PET is a carbonyl group, which is an organic functional group formed by connecting two atoms of carbon and oxygen through a double bond (C ═ O), and since the electronegativity of oxygen (3.5) is greater than that of carbon (2.5), the electron cloud distribution of the C ═ O bond is biased toward the oxygen atom: this feature determines the polarity and chemical reactivity of the carbonyl group. The chemical reaction characteristic of carbonyl is commonly applied in the chemical field, but there is little relevant applied literature in the physical field, the application of radio frequency to carbonyl polarity causes slight heating, the heating temperature can reach 80 ℃, the temperature is lower than the melting point of PET, but is close to the foaming temperature of 100-110 ℃, and from the foaming quality, the closer the temperature of the interior of the foamed rubber material is to the temperature of a mold, the better the fusion and fusion of the foamed material are.

And when 25% of glass fiber is added into the PET material, the molecular chain of the PET shows higher rigidity, so that the glass transition temperature and the melting point of the PET are higher, and the PET has excellent mechanical properties. All groups on a PET molecular chain are orderly arranged, a macromolecular chain is regular, all benzene rings on the molecular chain are almost not on the same plane and are in a plane fluctuation shape, concave and convex parts of different molecular chains are embedded, and the packing density of PET is higher. Therefore, the PET mould with 25% of glass fiber has excellent mechanical property, better elasticity and impact resistance, and the 25% glass fiber reinforced PET mould has strong toughness, and the impact strength of the PET mould can be comparable to that of an aluminum alloy mould and is 3-5 times that of other plastics. The thermal deformation temperature of PET which is not reinforced by glass fiber is only 85 ℃; the melting point is 225-260 ℃ (depending on the crystallinity), and the glass transition temperature is 69 ℃; the thermal deformation temperature of the reinforced PET is 220 ℃, and the PET mould with 25% of glass fiber can be used for a long time at the temperature of 120-150 ℃, and is suitable for the material selection at the foaming temperature of 100-110-.

The properties of the nylon material are different from those of the PET material, but through experiments, the radio frequency slightly heats the nylon mold, and the nylon molecular chain contains polar group amide groups (-NHCO-), which are typical polar crystalline high molecular polymers. Because the polar acylamino in the main chain of the nylon molecule is an easily water-absorbing group, the foaming material of the invention selects one or more of water, hydrogen peroxide, ethanol and alkali liquor as polar medium materials, and all contain water molecules, the nylon which is not conductive per se is conductive after absorbing water, and the conductive nylon can enhance the heating effect of radio frequency on the nylon mold, so that the nylon mold can be heated to 100-110 ℃, and the foaming temperature tends to be 100-110 ℃. And the temperature is increased to 100-110 ℃ which is far lower than the melting point of the nylon per se, namely 215-260 ℃, so that the use of the nylon mold is safe and reliable, and the fusion welding and fusion of the foaming material have better effect.

Similarly, the 25% glass fiber is added for reinforcing the nylon mold, because the nylon mold of the 25% glass fiber reinforced nylon 66 is matched with the aluminum alloy in mechanical property, the tensile strength can reach more than 1500, and the tensile strength of the duralumin and the aluminum alloy is between 1500-1600, so the 25% glass fiber reinforced nylon mold is equivalent to the aluminum alloy mold in mechanical property. 25% fiberglass reinforced nylon was chosen because only 25% content of fiberglass reinforced nylon has the best properties and a more attractive surface.

Although both PC and PTFE can be used for manufacturing the mold, the PC and PTFE are non-polar materials, so that no self-heating function is generated under the action of radio frequency, and relatively speaking, when the foaming temperature of the foam rubber material is 100-110 ℃, the temperature of the mold is not changed, and the mold has no positive effect on the fusion welding and fusion of the foam rubber material. In particular, rf heating is from the inside out, with the surface heating being the least effective. Tests show that the mold made of Polytetrafluoroethylene (PTFE) is difficult to realize the welding quality of the surface of the product, so that the product has good welding quality. PC and PTFE molds require preheating to solve the problem, and the addition of preheating adds significant complexity to the overall rf process, and is time consuming in addition to the need to add a heat source (e.g., steam, hot oil, hot air, or other hot medium) to heat the PC and PTFE molds. Therefore, the selection of the simple cleanliness, efficiency, cost and yield of the die is far inferior to that of PET plus 25% glass fiber and nylon plus 25% glass fiber.

In order to make up the temperature difference between a mold and a foaming material when PET and 25% glass fiber are added in radio frequency foaming, the following method is adopted: and heat-conducting fillers are added into the upper die 2 and the lower die 3, the heat-conducting fillers are talcum powder, and the heat-conducting fillers are unevenly distributed in the upper die 2 and the lower die 3, so that heat transfer is facilitated, the temperature of the die is increased, and the temperature of the die is closer to the foaming temperature of the material.

Taking a PET and 25% glass fiber mold as an example, when the heat-conducting fillers are unevenly distributed on the PET material layer, the PET material layer comprises a high-content heat-conducting filler PET layer and a low-content heat-conducting filler PET layer, the PET material near the product cavity contains more heat-conducting fillers, which is called the high-content heat-conducting filler PET layer, and the PET material near the upper die electrode 4 or the lower die electrode 5 contains less heat-conducting fillers, which is called the low-content heat-conducting filler PET layer. In the invention, the diameters of the two heat-conducting fillers on the low-content heat-conducting filler PET layer and the high-content heat-conducting filler PET layer are different, the diameter of the particle heat-conducting filler of the high-content heat-conducting filler PET layer is preferably less than 15 mu m and is called as a first heat-conducting filler 19, and the diameter of the particle heat-conducting filler of the low-content heat-conducting filler PET layer is preferably 15 mu m-50 mu m and is called as a second heat-conducting filler 20.

As shown in fig. 2, after the PET mold is filled with the heat conductive fillers with different densities and particle sizes, the PET mold is also simultaneously an energy absorber, when the foaming material foams gradually to increase the temperature, the dense first heat conductive filler 19 with smaller particle size can absorb the heat of the foaming material quickly, and then the heat is conducted to the second heat conductive filler 20, so that the original PET mold without heat transmission is also increased in temperature, because the first heat conductive filler 19 with high density and small particle size has better heat absorption, and the second heat conductive filler 20 with low density and large particle size has better heat transmission/heat dissipation, thereby the temperature increase effect of the mold can be reached quickly, and the temperature of the mold is closer to the foaming temperature of the material.

Researchers have conducted the following experiments to demonstrate that the addition of the thermally conductive filler enhances the thermal conductivity of the mold, thereby increasing the temperature more quickly. The following experimental data comparison was made using PET plus 25% glass fiber as an example, see Table 1

Comparative example 1 shows that the thermal conductivity of the PET plus 25% fiberglass mold is very low.

Comparative example 2 shows that the thermal conductivity of PET plus 25% glass fiber mold can be improved by adding the thermal conductive filler with small particle size.

The comparison between the embodiment 1 and the embodiment 2 shows that the heat-conducting filler is added in two layers, the heat-conducting fillers with different particle sizes are selected, and the higher the heat conductivity coefficient of the PET and 25% glass fiber mold is. Thereby facilitating heat transfer and bringing the temperature of the mold as close as possible to the foaming temperature. After the improvement, the PET and 25% glass fiber mold containing the heat-conducting filler can reach a high temperature of 95-98 ℃, and the fusion welding and fusing quality of the foamed rubber material is obviously improved.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A novel foaming glue forming process is characterized by comprising the following steps:

s1, preparing a radio frequency foaming mold, wherein the radio frequency foaming mold comprises a radio frequency generator (1), an upper mold (2), a lower mold (3), an upper mold electrode (4) and a lower mold electrode (5), the upper mold (2) and the lower mold (3) are opposite to each other and can be opened and closed, when the upper mold (2) and the lower mold (3) are closed, a product cavity (15) is formed, the upper mold electrode is installed on the upper mold, the lower mold electrode is installed on the lower mold, the radio frequency generator (1) is electrically connected to the upper mold electrode (4) through an upper mold radio frequency conducting wire (13) and is electrically connected to the lower mold electrode (5) through a lower mold radio frequency conducting wire (14), the product cavity (15) is communicated with a foaming glue raw material system (16) through a filling gun (6), is communicated with a vacuum system (17) through a vacuum pipeline, and is communicated with a compression air system (18) through a forming compression air pipeline (10), the other end of the compressed air system (18) is communicated to a filling gun (6) through a filling compressed air pipeline (11), and the front ends of the upper die (2), the lower die (3) and the filling gun (6) adopt polar non-metallic materials: the PET material added with 25 percent of glass fiber and heat-conducting filler or the nylon material added with 25 percent of glass fiber; the heat-conducting fillers are talc powder, the heat-conducting fillers are unevenly distributed in the upper die (2) and the lower die (3), when the heat-conducting fillers are unevenly distributed in the PET materials, the PET material layer comprises a high-content heat-conducting filler PET layer and a low-content heat-conducting filler PET layer, the PET materials close to the product cavity contain more heat-conducting fillers and are called high-content heat-conducting filler PET layers, the PET materials close to the upper die electrode (4) or the lower die electrode (5) contain less heat-conducting fillers and are called low-content heat-conducting filler PET layers, the two heat-conducting fillers on the low-content heat-conducting filler PET layer and the high-content heat-conducting filler PET layer are different in particle size, and the particle heat-conducting fillers on the high-content heat-conducting filler PET layer are smaller than the particle heat-conducting fillers on the low-content heat-conducting filler PET layer;

s2, die filling and die assembly;

s4, tightly buckling a metal hood in the foaming mold equipment to ensure that radio frequency electric waves cannot leak;

s5, filling, and enabling the mixture A to enter a product cavity (15) in a vacuum and/or negative pressure mode;

s7, performing radio frequency heating, opening a forming compressed air system (18), starting the radio frequency heating according to the machine adjusting parameters of the step S6, generating radio frequency waves through a radio frequency generator (1), applying the radio frequency waves to the mixture A, rapidly heating the mixture A to 100-110 ℃, and fusing the foamed adhesive particles into a whole under the condition; after the radio frequency heating is finished, the forming compressed air is closed;

and S9, opening the die and taking out the product.

2. The novel foam rubber molding process according to claim 1, characterized in that: the foamed collagen material in step S3 includes: expanded polystyrene EPS, expanded polystyrene-polyethylene mixed EPO, expanded polypropylene EPP and expanded polyethylene EPE.

3. The novel foam rubber molding process according to claim 2, characterized in that: the polar medium materials include, but are not limited to: one or more of water, hydrogen peroxide, ethanol and alkali liquor.

4. The novel foam rubber molding process according to claim 1, characterized in that: the output frequency of the radio frequency generator is radio frequency with frequency of 13.35MHZ or 27.12MHZ, sine waves or pulses with power of 1 KW-30 KW act on the upper die electrode (4) and the lower die electrode (5), and the positive and negative electrodes of the upper die electrode (4) and the lower die electrode (5) are always in an alternating state.

5. The novel foam rubber molding process according to claim 1, characterized in that: the upper die electrode (4) and the lower die electrode (5) are made of aluminum plates without sharp corners.

6. The novel foam rubber molding process according to claim 1, characterized in that: before foaming, the compressed air system inputs about 1-2 bar of pressure to the product cavity (15) to enable the foaming rubber particles to be attached tightly, and inputs about 30-40 bar of pressure to the product cavity (15) after foaming to enable the foaming product to be stripped.

7. The novel foam rubber molding process according to claim 1, characterized in that: is used for foaming and forming helmets.