JPS6045168A - Manufacture of expanded silicon packing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a foamed silicone backing, and particularly to a method for producing a foamed silicone backing that is suitable for use in food containers and is resistant to mold growth.

BACKGROUND ART Puffing has conventionally been used to provide an effective seal by being interposed between the abutting portions of two members to prevent or prevent the passage of liquid or gas between them. Foamed silicone backings, which are made of silicone foam, are often used as backing materials for food containers due to their excellent elastic recovery properties, heat resistance, and cold resistance. It is becoming.

However, in such foamed silicone packing, mold forms during its use, and especially when used for food containers, there is a problem in that mold tends to grow on the surface of the packing. The problem of mold growth is a major problem that must be solved in order to extend the service life of the bagging.

Here, as a result of various studies in view of the above circumstances, the inventors of the present invention found that foamed silicone packing has no traces of air sacs (cells) generated by foaming on the surface. It looks like a tiny cave-like hole (opening)
It has been confirmed through microscopic observation that there are a large number of It was discovered that mold grows using food particles that have entered the unevenness of the backing surface as a nutrient source.

Therefore, the inventors of the present invention conducted further studies and found that foamed silicone packing, which has been treated to have a smooth surface so that food-borne substances can be easily washed off, has been developed. The inventors discovered the fact that the nutrient source for the mold is lost, and therefore the mold grows and the mold grows), and has now completed the manufacturing method of foamed silicone packing with improved surface properties according to the present invention. It is.

That is, the present invention provides a method for producing a seal that is interposed between the abutting portions of two members to form a seal between them, and in which liquid silicone is applied to a silicone foam molded into a predetermined shape. The present invention provides a method for producing foamed silicone packing, which is characterized in that a skin layer of a predetermined thickness of non-foamable silicone is formed on the surface of the silicone foam by coating the silicone foam with a heat-drying treatment.

As described above, the method for manufacturing foamed silicone foam according to the present invention is to further form a bubble-free silicone skin layer by heating and drying the liquid silicone coating on the surface of the silicone foam. Therefore, the skin layer covers the cell openings existing on the surface of the foam, thereby eliminating unevenness on the surface of the foam, and there is no place for food particles to enter and remain. If food particles, etc. adhere to the surface of such a backing, such food particles, etc., can be easily and reliably washed and removed by normal cleaning operations, thereby eliminating the source of mold. 9JJ was successfully removed, and as a result, a clean foamed silicone backing free from mold growth could be provided.

By the way, in order to obtain the foamed silicone backing 1 according to the method of the present invention, it is first necessary to mold a silicone foam in a predetermined shape in the same manner as in the conventional method. For molding this silicone foam, for example, a 1:1 silicone rubber base (compound) as a basic abrasive, henzoyl perogizide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, etc. A vulcanizing agent such as peroxides and a blowing agent such as abbisisobutyronitrile are respectively blended.

In general, the proportion of the vulcanizing agent is about 0.5 to 5 parts by weight, and the blowing agent is about 1 part by weight per 100 parts by weight of the base material.
~4 parts by weight.

The basic composition and the vulcanizing agent and blowing agent as additives are blended using a suitable kneading machine, for example, a two-roll (
The process is carried out using an open roll (open roll), and the materials are generally introduced in the order of basic material (silicone rubber raw material), blowing agent, and vulcanizing agent. Also, during this kneading process, equipment such as rolls should be sufficiently cooled.
It is desirable that the temperature of the kneaded product is below the decomposition starting temperature of the vulcanizing agent blended, and the kneading time is also
As in the past, it will be determined as appropriate, taking into account the heat of mixing and the like.

Next, the kneaded material is as shown in FIG.
It is extruded from a suitable extruder 2 to form a predetermined continuous extrudate 4, and the extrudate 4 is introduced into a vulcanization tower 6 where it is heated at a predetermined temperature (e.g. 300 to 310°C) for a predetermined time (e.g. 1 to 2 minutes), vulcanization and foaming of the extrudate 4 to be darned is induced,
The desired silicone foam 8, that is, a molded product of foamed silicone rubber, is continuously obtained and taken up by the taking-off machine 1o. This silicone foam 8
The shape generally corresponds to the shape of the extrudate 4, which is controlled by an extrusion die attached to the extruder 2, and the product shape also depends on the heating temperature and material passage time in the vulcanization tower 6, in other words. This will be determined by the vulcanization and foaming conditions.

The silicone foam (silicone sponge) is formed by a foaming phenomenon caused by the timing at which the vulcanizing agent and foaming agent in the extrudate 4 decompose in the vulcanizing tower 6. That is, 2 as the vulcanizing agent
．． 4 - The decomposition temperature of dichlorohendyl peroxide is around 110'C, dicumyl peroxide is around l30'C, and the blowing agent azobisisobutyronitrile is around 100°C. This is because they have different decomposition temperatures, and their decomposition rates are also different. Microscopically, the former vulcanizing agent begins to decompose gradually at around 60°C and the latter at around 80°C, but the foaming agent decomposes rapidly at 100°C. be. Therefore, if the temperature is kept below the decomposition temperature of the vulcanizing agent during kneading, and the temperature is kept above the decomposition temperature of the blowing agent in the vulcanizing tube, when the silicone becomes rubber-like due to the vulcanizing agent, N2 gas will be released due to the decomposition of the blowing agent. This occurs, and many air bubbles are formed inside, resulting in the formation of a spongy rubber. In addition, after the sponge is formed, the N2 gas generated inside the bubble film (
It passes through the cell membrane (rubber membrane) and diffuses.

Of course, such a foaming process is appropriately selected depending on the type of vulcanizing agent and blowing agent used, the vulcanization foaming conditions in the vulcanization tower 6, etc. It will be designed to give a body (sponge).

Further, after the generally continuous longitudinal silicone foam 8 formed in this way is taken up by a take-up machine 10, the undecomposed vulcanizing agent remaining inside it is decomposed and vulcanized. In order to remove the decomposition products of the foaming agent and the foaming agent, a secondary vulcanization operation (bost cure or aging operation) is performed at a temperature of 120 to 180°C for 3 to 8 hours in the same manner as in the past.
It will be carried out under the condition of time.

In the silicone foam 8 thus obtained, the second
As shown in the figure and FIG. 3, the cells 12 formed inside are independent bubbles and are discontinuous, and their surfaces are extremely flat from a macroscopic perspective. When viewed microscopically, as shown in FIG. 3, some of the many cells existing in the surface layer are open cells 14 where the silicone membrane has been torn, and this causes the foam 8 to This is because the surface is uneven.

Due to the presence of such open cells 14, when the silicone foam 8 is used for banking, food particles may enter and accumulate there, resulting in stains that are difficult to remove even by cleaning. , such dirt makes it easier for mold to grow.

Therefore, in the present invention, a skin layer made of a predetermined non-foamable silicone is formed on the surface of the silicone foam 8 to be bent, and such a skin layer is formed as shown in FIG. It is effectively formed according to the method and equipment shown in .

That is, in FIG. 4, a continuous longitudinal silicone foam 8 is guided into an immersion tank 2o containing a predetermined liquid silicone 18 while being made to travel in its longitudinal direction via a guide roller 16. Then, a predetermined amount of liquid silicone 18 is deposited on the surface according to the guide by the immersion roller 22, and the 'IN? It is designed to be taken out from the M tank 2o.

This liquid silicone 18 forms a skin layer made of non-foaming silicone (without bubbles) on the surface of the silicone foam 8, and is based on, for example, silicone rubber or its raw material, and is made of toluene, A solution obtained by dissolving and jellying with a solvent such as xylene or naphtha is used. The appropriate blending of a solvent with the silicone base material adjusts the viscosity of the liquid silicone 18 and at the same time causes the surface layer of the silicone foam 8 to swell with the solvent, allowing the liquid silicone 18 to penetrate or enter the open cells 14. It makes it easier to get in. Furthermore, the silicone foam 8 is made of silicone foam so that the skin layer formed by applying the liquid silicone 18 will not be torn even if the banking manufactured according to the present invention is stretched during actual use. The silicone base material of the liquid silicone 18 is appropriately selected so as to have the same or higher elongation (flexibility).

Next, the liquid silicone 18 is soaked in the dipping tank 20 in this way.
The silicone foam 8 coated with
The material is guided into the interior and is heated and dried while traveling inside the interior.

Drying in the dryer 24 is carried out by circulating hot air (for example, about 140 to 150°C) from top to bottom as shown by the arrow in the figure, while the liquid silicone 18 is applied by an upper drive roller 26. This is carried out by continuously pulling up the silicone foam 8, and by the time it reaches the drive roller 26 it is almost dry to the touch.

That is, the silicone foam 8 is exposed to the hot air flowing from the top to the bottom, the temperature of which gradually increases from about Zy80°C at the bottom, thereby effectively drying it. be. Furthermore, the silicone foam 8 that has passed through the drive roller 26 is further exposed to hot air to be more completely dried.
Then, it is taken out from the lower part of the dryer 24 and taken as a product via guide rollers 28 and 30.

Note that the drying conditions (temperature: 1 hour) in this dryer 24 will be appropriately determined depending on the properties of the liquid silicone 18, such as the type of solvent, etc. The foam 8 is
Drying by exposure to hot air at progressively higher temperatures is desirable in forming the skin layer according to the present invention.

Then, by this heating drying operation, liquid silicone 1
8 forms a skin layer on the surface of the silicone foam 8 since it is made of non-foaming silicone. That is, as shown in FIGS. 5 and 6, a skin layer 32 of non-foamable silicone is formed over the entire surface of the silicone foam 8 to a predetermined thickness. The open cells 14 on the surface of the foam 8 are covered, and the open cells 14 substantially on the surface of the foam 8 are prevented from opening, so that the surface is extremely flat and has no irregularities. It is said that

Further, as described above, such skin N32 is made of foam 8 made of a solvent mixed with liquid silicone 18.
``Due to the swelling action of the surface layer, it bites into the surface of the silicone foam 8 and is integrated with it, forming fine open cells 14.
(See Figure 6), which significantly enhances their adhesion. The skin F232 thus formed on the surface of the silicone foam 8 can be formed with various thicknesses depending on the purpose, but generally it is formed with a thickness of about 20 to 100μ. Become.

and the thus obtained predetermined silicone skin N
Silicone foam 8b1 provided with 32. When a solvent is used in the skin layer forming process, a deodorizing process (for example,
The foamed silicone backing is then subjected to a powder coating process to prevent tack on the surface (for about 1 hour), followed by a predetermined finishing process to form the desired foamed silicone backing. It is.

The thus obtained silicone foam 8 on which a skin layer made of non-foamable silicone is formed has no unevenness on its surface, in other words, the openings of the open cells 14 are covered with the skin layer 32. Since the surface is smooth, there is no place for food particles to enter, and therefore it can be easily and reliably cleaned by normal cleaning operations, eliminating the source of mold. Therefore, the occurrence of mold, etc. can be effectively eliminated.

Moreover, according to the preferred method of the present invention, the skin layer 32
As mentioned above, it is firmly integrated with the silicone foam 8 and also has sufficient elongation (flexibility).
Even if it is stretched during actual use, the skin layer 3
This makes it possible to produce a useful foamed silicone backing as described above that has a durable skin layer 32 without tearing or peeling.

Therefore, the silicone foam 8 having the skin layer 32 according to the present invention is extremely useful as a foamed silicone backing.For example, as shown in FIG. In a container, it is advantageously used as a backing 38 that is interposed at the mating part (abutting part) of the container, and the backing has the original effect, that is, it is sandwiched between the lid 34 and the container body 36,
This prevents liquid or gas from leaking between them, and even if food particles or the like are attached to the backing 38, it can be easily removed by a simple cleaning operation, and mold or the like will not grow there. This has made it possible to permanently maintain the cleanliness required of food containers.

Although specific examples of the present invention have been described in detail above, the present invention is not to be construed as being limited to such specific examples, and various modifications and changes may be made without departing from the spirit of the present invention. It is possible to make corrections, improvements, etc.

For example, the foamed silicone backing according to the present invention can be molded into various shapes depending on its use, and even in the step of forming the skin layer, only the continuous forming method as illustrated is possible. Instead, it is also possible to adopt a method of applying liquid silicone in a batch process and drying it without running the silicone foam 8. Moreover, it can also be applied to items other than food containers.
It is possible to apply foamed silicone banking according to the invention.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing the manufacturing process of the silicone foam according to the present invention, FIG. 2 is a perspective view of the silicone foam, and FIG. 3 is an enlarged cross-sectional view showing the state of the surface layer of the silicone foam. FIG. 4 is a system diagram showing the process of forming a skin layer on a silicone foam, and FIG.
The figure is a sectional view showing an example of the foamed silicone backing obtained by the present invention, FIG. 6 is an enlarged explanatory view of its surface layer, and FIG. 7 is a food product equipped with the foamed silicone backing obtained by the present invention. FIG. 2 is a perspective view (partially cut away) showing the container. 2: Extruder 6: Vulcanizing group 8: Silicone foam] 2: Cell 14: Open cell 18: Night-like silicone 20: Dipping tank 22: Dipping roller 24: Dryer 26: Drive roller 32 Niskin layer 34: Lid Body 36: Container body 38: Packaging Applicant: Chopla Industries Co., Ltd. Nissei Electric Co., Ltd.

Claims (1)

[Claims] (1) A method of equipping a backing that is interposed between the abutting portions of two members and performs a seal between them, for silicone foam formed into a predetermined shape. 1. A method for producing a foamed silicone backing, which comprises coating a silicone foam with liquid silicone and then heating and drying it to form a skin layer of a predetermined thickness of non-foaming silicone on the surface of the silicone foam. (21fiii) The manufacturing method according to claim 1, wherein the liquid silicone is applied to the silicone foam in a state dissolved in a predetermined solvent. (3) The silicone foam has a continuous longitudinal shape. While running in the longitudinal direction, the liquid silicone was passed through a tank containing the liquid silicone, and then led into a predetermined heating and drying chamber where it was exposed to hot air whose temperature was gradually raised. The manufacturing method according to claim 1 or 2. (4) A patent in which the two members are composed of a lid and a container body, and the lid and the container body constitute a food container. A manufacturing method according to any one of claims 1 to 3.