JP2004300302A - Latex foam and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a latex foam capable of exhibiting a prescribed adhesion without using an environmental pollutant such as formaldehyde by mixing a carboxy-modified latex rubber with a latex rubber of a main raw material, gelatinizing the obtained mixed latex rubber, and heating and hardening the latex rubber; and to provide a method for producing the latex foam. <P>SOLUTION: The latex foam is obtained by mixing a natural, synthetic or both-mixed latex rubber 22 of the main raw material, with the carboxylated modified latex rubber 24 having ≥-30°C glass transition temperature, a gelatinizing agent, a foam stabilizer and other required auxiliary materials to provide a latex foam raw material M, and crosslinking and hardening the latex foam raw material M. The latex foam having both of an charge adhesive effect exhibited by the modified latex rubber and a structural adhesive effect possessed by the latex foam, and exhibiting a high adhesive effect is produced without using/exhausting the environmental loading material such as the formaldehyde by crosslinking and curing the raw material of the latex foam obtained by mixing the carboxylated modified latex rubber having ≥-30°C glass transition temperature, with the usually used natural, synthetic or both-mixed latex rubber being a main material of the obtained latex foam. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３３】
（実施した測定およびその評価法）
・硬度：ＪＩＳ Ｋ ６３０１に準拠したＡＳＫＥＲ Ｆ型により測定した（使用硬さ試験機：商品名；ＣＬ−１５０；高分子計器製）。
・引張強さ：得られたラテックスフォームから厚さ３ｍｍの１号形試験片を作製し、該試験片の両端を離間するように引っ張って、その際の最大荷重（Ｎ）から測定する（使用引張試験機：商品名；ＡＧＳ−５ｋＮＢ；島津製作所製）。
・ 粘着性：
１．得られたラテックスフォームを６０ｍｍ×７０ｍｍの大きさにカットして試験片とし、これをロードセルの定盤に該試験片の測定対象面の反対面を両面テープ等を使用して固定させる。
２．引張試験機（商品名；ＡＧＳ−５ｋＮＤ；島津製作所製）のチャックに取り付けられた５３０ｇ、５０φの荷重錘を前記試験片上面（測定対象面）に３０秒載置する。
３．前記測定対象面に粘着状態となった荷重錘を引張スピード２００ｍｍ／ｍｉｎで連続的に引き上げ、該測定対象面と荷重錘とが離れる際の荷重を粘着性とする。なお、前記荷重錘の荷重は、測定荷重より差し引くものとする。また本実施例における製造方法においては、得られるラテックスフォームには平滑性が高い表面（シート体側の面：表中では第１面と呼称する）と、他方の面との２つの表面（表中では第２面と呼称する）があるが、その双方について粘着性を測定した。
【００３４】
（結果）
得られた各測定結果等を上記表１に併記する。そして得られた結果より、主原料をなすラテックスゴムと、カルボキシル化させた変性ラテックスゴムとの混合割合を８０：２０〜２０：８０の範囲とすることで、良好な粘着性、すなわちアクリル樹脂から製造した粘着性シートの少なくとも９０％程度の粘着性を発現しつつ、かつ該アクリル樹脂から製造した粘着性シートに較べて２．５〜４倍程度の引張強度を発現するラテックスフォームが得られることが確認された。殊に主原料をなすラテックスゴムと、カルボキシル化させた変性ラテックスゴムとの混合割合が５０：５０の時に最も良好な粘着性を示し、かつ該両ラテックスゴムが夫々１００％の時には粘着性が極めて低いことから、低い硬度の達成により発現する構造的な粘着効果と、変性ラテックスゴムの存在により発現される電荷的な粘着効果との双方のバランスが重要であることが示唆されている。更に第２面については、第１面の粘着性と較べて１／１０の粘着性しか発現されておらず、ここから得られるラテックスフォームの表面平滑性も重要であることが確認された。なお、環境負荷物質の１つであるホルムアルデヒドについてはＪＩＳ Ａ ６９２１に準拠した測定の結果、検出はされなかった。
【００３５】
【発明の効果】
以上説明した如く、本発明に係るラテックスフォームおよびその製造方法によれば、通常に使用され、得られるラテックスフォームの主材料となる天然または合成或いはこれらを混合させたラテックスゴムと、そのガラス転移点が−３０℃以上であり、カルボキシル化させた変性ラテックスゴムとを混合して得たラテックスフォーム原料を架橋・硬化させるようしたので、ホルムアルデヒド等の環境負荷物質を使用・排出することなく、該変性ラテックスゴムにより発現される電荷的な粘着効果と、ラテックスフォームが有する構造的な粘着効果とを併有して高い粘着効果を発現するラテックスフォームを製造し得る。
【００３６】
また、ラテックスフォーム自体が粘着性を発現するため、該ラテックスフォーム自体の優れた機械的強度を生かすことが可能であり、一度粘着させる等使用したラテックスフォームを強制的に剥離するに際して、該フォーム構造の破損を大きく抑制することが可能となり、再使用を容易とする効果を奏する。更に通常のラテックスフォーム製造に供する原料にカルボキシル化させた変性ラテックスゴムを混合することで製造が可能なので、従来通常に使用していたラテックスフォームの製造装置等で好適な製造が可能である。
【図面の簡単な説明】
【図１】本発明の好適な実施例に係るラテックスフォームの表面部分を拡大して示す断面図である。
【図２】実施例に係るラテックスフォームにおけるセル径と、構造的な粘着効果との関係を示す概略図である。
【図３】実施例に係るラテックスフォームの製造工程を示すフローチャート図である。
【図４】実施例に係るラテックスフォームの製造装置の一例を示す概略図である。
【符号の説明】
１４ セル
２２ ラテックスゴム
２４ 変性ラテックスゴム
Ｍ ラテックスフォーム原料[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a latex foam and a method for producing the same, and more specifically, a latex rubber (hereinafter simply referred to as a latex rubber) and a carboxylated modified latex rubber (hereinafter, referred to simply as a latex rubber) obtained by mixing natural or synthetic or a mixture thereof. By using carboxyl-modified latex rubber) as a main raw material, a latex foam which has an extremely low environmental load, has sufficient strength to be able to be reused, and exhibits required adhesiveness, and It relates to a manufacturing method.
[0002]
[Prior art]
For example, a so-called adhesive foam is suitably used as a fixing member such as a base material of a double-sided tape or a floor material represented by a flooring. The adhesive foam itself has a predetermined adhesiveness, and is a member that exhibits excellent cushioning, soundproofing, and vibration damping properties because the structure is a foam structure. It was indispensable.
[0003]
The adhesive foam is generally manufactured by the following method. That is,
{Circle around (1)} A foam is produced from a main material such as latex rubber constituting the foam, and a pressure-sensitive adhesive exhibiting required tackiness is separately applied to the surface of the obtained foam.
{Circle around (2)} A predetermined amount of a required pressure-sensitive adhesive is mixed with a main raw material such as latex rubber constituting the foam, and a foam is produced from the obtained mixed raw material.
{Circle around (3)} Acrylic resin having self-adhesiveness is adopted as a main raw material constituting the foam.
[0004]
[Problems to be solved by the invention]
However, the following disadvantages are pointed out in each of the above methods. That is,
{Circle around (1)} A step for separately applying a pressure-sensitive adhesive to the foam surface is required, and the production process of the foam becomes complicated. Further, since the pressure-sensitive adhesive exhibiting tackiness exists only on the surface of the foam, the tackiness is lost due to physical contact such as rubbing or washing of the surface.
{Circle around (2)} A step of separately adding a pressure-sensitive adhesive is required, and it is pointed out that the addition of the pressure-sensitive adhesive may change the production conditions of the foam and inhibit the development of other physical properties required for the foam. Furthermore, the part of the pressure-sensitive adhesive that exhibits actual tackiness is only the one located on the surface of the obtained foam, and it is necessary to add even the pressure-sensitive adhesive that does not contribute to the development of tackiness.
{Circle around (3)} The acrylic resin exhibits self-adhesion by methylol crosslinking such as melamine crosslinking and epoxy crosslinking, and formaldehyde is essential as a crosslinking agent for forming both crosslinked structures. It is a substance that has a large adverse effect on the human body, and its use is greatly restricted. Also, foams obtained from the acrylic resin have low mechanical strength compared to the developed adhesiveness. As a result, when the foam is peeled off from an adhesive object, for example, the foam itself is broken, and It is pointed out that it cannot be used.
[0005]
[Object of the invention]
The present invention has been proposed in view of the above-mentioned drawbacks inherent in the prior art latex foam and the method for producing the same, and has been proposed in order to preferably solve the problem. Latex foam capable of expressing predetermined adhesiveness by mixing modified latex rubber, gelling the obtained mixed latex rubber, heating and curing, without using environmental pollutants such as formaldehyde, and a method for producing the same The purpose is to provide.
[0006]
[Means for Solving the Problems]
In order to overcome the above-mentioned problems and achieve the intended purpose, the latex foam according to the present invention comprises a latex rubber comprising at least a natural or synthetic raw material or a mixture thereof, a gelling agent, a foam stabilizer and the like. In a latex foam obtained by crosslinking and curing a latex foam raw material mixed with required auxiliary materials,
It is characterized in that the latex rubber as the main raw material is mixed with a carboxylated modified latex rubber having a glass transition point of -30 ° C or higher.
[0007]
In order to overcome the above-mentioned problems and achieve the intended purpose, a method for producing a latex foam according to another invention of the present application includes a latex rubber composed of a natural or synthetic material or a mixture thereof, which is a main raw material, and a glass transition point thereof. -30 ° C or higher, mixed with a carboxylated modified latex rubber,
To 100 parts by weight of the obtained mixed latex rubber, 1.0 to 5.0 parts by weight of a foam stabilizer and required auxiliary materials are mixed to form a liquid material,
To 100 parts by weight of this liquid material, a gelling latex foam material was obtained by mixing 1 to 10 parts by weight of a gelling agent,
The cross-linking / curing is advanced by heating the gelled latex foam raw material.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, a latex foam and a method for producing the same according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments. The inventor of the present application has determined that a carboxylated modified latex rubber having a glass transition point of −30 ° C. or higher is contained at a predetermined ratio with respect to a natural or synthetic latex rubber which is a main raw material constituting a latex foam or a mixture thereof. By mixing, the high mechanical strength of the latex foam and the charge possessed by the carboxyl group of the modified latex rubber and the adhesiveness suitably expressed by the semi-closed cell structure of the obtained latex foam, It has been found that a latex foam which can be used over a wide range as a general adhesive material without environmental load can be obtained.
[0009]
As shown in FIG. 1, a latex foam 10 according to a preferred embodiment of the present invention has a latex rubber (hereinafter referred to as a latex rubber) 22 as a main raw material or a mixture thereof, and a carboxylated modified latex. The skeleton 12 includes a latex rubber (hereinafter, referred to as a carboxyl-modified latex rubber) 24 and a cell 14 formed by a gas such as air (the details will be described later in [0021]). Then, a charge-sensitive adhesive effect developed by the negative charge of the carboxyl group (functional group) of the carboxyl-modified latex rubber 24 (conceptually illustrated by a minus sign in FIG. 1). A good adhesive effect is obtained by a synergistic effect with the structural adhesive effect expressed by the so-called sucker (negative pressure) action of the semi-cellular structure of the obtained latex foam 10. The charge adhesion effect and the structural adhesion effect increase with the degree of approach of charge and the degree of retention of the negative pressure state in the cell 14, that is, the degree of adhesion between the latex foam 10 and the adherend. Things.
[0010]
Regarding the above-mentioned structural adhesive effect, (1) the magnitude of the strength is pseudo-expressed by the product of the total number of cells 14 open to the outside and (2) the internal volume of the cells 14. Is possible. Here, (1) the total number of cells 14 open to the outside represents the total number of cells 14 involved in the suction function, and (2) the internal volume of the cells 14 It can be regarded as an index that indicates a possible air amount, that is, the strength of the suction cup effect that one cell 14 exhibits. On the other hand, when the structure of the cell 14 is a closed cell structure, (1) and (2) are determined only by the size of the cell 14, and as shown in FIG. 1) increases while (2) decreases (see FIG. 2 (a)), whereas if it is large, (1) decreases while (2) increases (see FIG. 2 (b)). It can be said that it is extremely difficult to maintain both (1) and (2) at a high level. This is obvious because the volume of the latex foam 10 is finite, so that the internal volume of the cell 14 and the number of the cells 14 are inversely proportional. In addition, in the case of the latex foam 10 according to the present invention, the size of the cell 14 can be arbitrarily controlled by the time for gelling the two latex rubbers 22 and 24 forming the skeleton, that is, the amount of the gelling agent added. There is no particular problem because of this, but if it is too large, the above-mentioned (1) is reduced, so that it is preferable that the thickness be 500 μm or less.
[0011]
The latex foam 10 is suitably manufactured through the steps shown in FIG. This step basically includes a raw material adjusting step S1, a gelling step S2, a heating step S3, and a final step S4. Further, the respective steps S1 to S4 are suitably performed by the manufacturing apparatus 30 as shown in FIG. The manufacturing apparatus 30 continuously manufactures the sheet-like material 20 which is the base of the latex foam 10 having a required shape from the gelled latex foam raw material M obtained through the raw material adjusting step S1 and the gelling step S2. It is a device to do. Note that the gelled latex foam raw material M and the gelled latex foam raw material M described below do not only refer to the raw material completely gelled, but are added in the gelling step S2. The raw material in the course of gelation and the completely gelled raw material from the liquid latex foam raw material (hereinafter referred to as a liquid raw material, hereinafter referred to as [0013]) obtained in the raw material preparation step S1 by the gelling agent It points.
[0012]
Specifically, the manufacturing apparatus 30 includes a mixing mechanism 32 that performs the raw material adjustment step S1 to obtain a liquid raw material, and a transfer belt 36a that is driven by a drive source (not shown) for transferring the gelled latex foam raw material M. And a belt conveyor type transfer mechanism 36 having the following. The gelling step S2 is arranged at the most upstream side of the transfer mechanism 36, and the latex foam raw material M gelled on the transfer belt 36a is continuously transferred. A mixing head 34 to be supplied, a product thickness control means 38 provided downstream of the mixing head 34 to form the supplied gelling raw material into a sheet having a predetermined thickness, and a predetermined length provided downstream thereof. It is basically composed of a tunnel heating furnace 40.
[0013]
(About raw material adjustment step S1)
The raw material adjusting step S1 performed by the mixing mechanism 32 is a step for mixing and stirring each raw material of the latex foam 10 to be obtained to obtain a liquid latex foam raw material (liquid raw material). It comprises a first mixing step S11 of mixing 22 and 24 to obtain a mixed latex rubber, and a second mixing step S12 of mixing the obtained mixed latex rubber with another auxiliary material. Specifically, among the raw materials for obtaining the latex foam 10, substances other than a gas such as a gelling agent and air forming cells, that is, a natural or synthetic main material or a latex rubber 22 obtained by mixing these, In a separate step, the carboxyl-modified latex rubber 24 that has been carboxyl-modified in advance is mixed with auxiliary materials such as a vulcanizing agent, a vulcanization accelerator, a foaming agent, a foam stabilizer, an antioxidant, and the like, which are crosslinking agents. Then, a liquid raw material is obtained by mixing these substances.
[0014]
As the latex rubber 22 which is a main raw material of the latex foam 10, a natural or synthetic latex rubber such as NBR latex, SBR latex, chloroprene rubber (CR), NR latex rubber or ethylene-propylene-diene terpolymer (EPDM) is used. Used alone or as a mixture. As the physical properties of the latex rubber 22, it is desirable that the glass transition point is set to at least −50 ° C. or more, preferably in the range of −50 to 20 ° C. By setting the glass transition point, the characteristic properties of the carboxyl-modified latex rubber 24 mixed with the latex rubber 22, that is, the water content is large and the solid content is small, (1) gelation is difficult, and (2) ▼ The problem that the obtained latex foam exhibits high hardness can be efficiently avoided.
[0015]
Although the above-mentioned problem of (1) gelation can be avoided by increasing the amount of the gelling agent and coexistence of the latex rubber 22, this method also has the effect of increasing the hardness of the latex foam 10 obtained as described above. In view of both the problem of gelation (1) and the high hardness of (2), the latex foam 10 obtained generally has high hardness. If the hardness is too high, the so-called shape followability is greatly deteriorated, and the above-mentioned favorable manifestation of the charge adhesion effect and the structural adhesion effect is impaired. This occurs because the adherence between the obtained latex foam 10 and the adherend cannot be maintained due to the deterioration of the shape following property. Particularly, the deterioration of the shape following property is caused when the surface shape of the latex foam 10 does not match the shape of the surface to be adhered of the object to be adhered or when the surface to be adhered has low smoothness, for example, when the surface is irregular. It becomes remarkable.
[0016]
The glass transition point is a point at which the internal structure of the substance changes abruptly at that temperature. In the case of the two latex rubbers 22 and 24 in the present invention, the flexibility increases from the solid state with an increase in temperature, that is, The point is that the hardness is reduced and the so-called shape followability is improved. Therefore, the present invention prevents the deterioration of the shape following property by using the latex rubber 22 set to have a glass transition point capable of expressing high flexibility at normal temperature, that is, a glass transition point of 20 ° C. or less. are doing. If the temperature at the glass transition point is lower than -50 ° C, fluidity is exhibited at normal temperature, which is a normal use temperature range, and the resulting latex foam 10 cannot maintain its shape. As for the hardness, it is basically preferable that the latex foam 10 is flexible as long as it can maintain its shape. However, in the present embodiment, the hardness according to the measurement method described later ([0032]) is used. Is 50 or less, it has been confirmed that the above-described shape followability is good.
[0017]
As the carboxyl-modified latex rubber 24, NBR latex, SBR latex, a carboxyl-modified product of chloroprene rubber (CR), or a mixture of carboxyl-modified products of these latex rubbers is used. The mixing amount of the carboxyl-modified latex rubber 24 is set so that the weight ratio between the latex rubber 22 as the main raw material and the carboxyl-modified latex rubber 24 is 80:20 to 20:80. When the mixing ratio of the carboxyl-modified latex rubber 24 is less than 20, sufficient tackiness cannot be obtained in the finally obtained latex foam 10, and when it exceeds 80, the carboxyl-modified latex rubber described above ([0014]) Due to the properties of No. 24, it is difficult to obtain a suitable gel, and the hardness of the obtained latex foam is increased to reduce the shape following property. As a result, both the charge effect and the structural adhesive effect (the aforementioned [0010] ]) Cannot be expected.
[0018]
The glass transition point of the carboxyl-modified latex rubber 24 is set to at least −30 ° C. or higher. When the glass transition point is set to less than -30 ° C, high fluidity is exhibited in a normal temperature range, and as described above ([0016]), the obtained latex foam 10 cannot maintain its shape. . On the other hand, the upper limit of the glass transition point is not particularly set, but is preferably 20 ° C. or lower similarly to the latex rubber 22. If the glass transition point is too high, the above-described shape following property cannot be maintained in a favorable state, and as a result, the above-described charge-based adhesive effect and structural adhesive effect cannot be sufficiently exhibited. This point can be avoided by setting the glass transition point of the other latex rubber 22 mixed with the carboxyl-modified latex rubber 24 low, but on the other hand, the fluidity of the obtained latex foam 10 becomes high. Care must be taken because the shape may not be maintained.
[0019]
The degree of mixing in the first mixing step S11, that is, the degree of mixing of the carboxyl-modified latex rubber 24 (meaning the degree of dispersion of the carboxyl-modified latex rubber 24 in the latex rubber 22 as a main raw material) depends on the latex foam obtained. 10 is directly related to the degree of adhesion. If the mixing is not sufficiently performed, the charge adhesion effect described above ([0009]) cannot be achieved.
[0020]
Specifically, when a shearing force is applied to the latex rubber 22 and the carboxyl-modified latex rubber 24, which are the main raw materials, so that extra air bubbles are not entrained, mixing is preferably performed for about 30 minutes. I know from experience. The first mixing step S11 is performed at a shear rate of 10 to 10000 min. ^-1 It has been implemented to be. The maximum shear rate Q (min) that the mixing (stirring) equipment used can exhibit ^-1 ) Is defined as:
Q = (P × π × S) / V
here,
P: Blade diameter (mm) of stirring blade of mixing (stirring) device
π: 3.14 (pi)
S: Number of rotations per minute
V: distance (mm) of the narrowest part in the clearance (gap) between the mixing (stirring) device container and the mixing (stirring) blade
That is, a mixing (stirring) device in which each of the above elements is set so as to have a maximum shear rate at which the shear rate can be performed may be used.
[0021]
In the second mixing step S12, the respective auxiliary materials are added to the mixed latex rubber obtained in the first mixing step S11. This is the stage of mixing. The amount of each of the auxiliary materials is 0.5 to 6 parts by weight of a vulcanizing agent and a vulcanization accelerator as a crosslinking agent, and 2 to 6 parts by weight of a foaming agent, based on 100 parts by weight of the mixed latex rubber. Parts by weight, about 1.0 to 5.0 parts by weight of a foam stabilizer, and about 1 to 5 parts by weight of an antioxidant. Note that the types and amounts of the auxiliary materials are merely examples, and the auxiliary materials appropriately selected from conventionally known ones depending on the types of the main materials, the amounts of the materials adjusted at a time, and the like are necessary. Used only in quantity.
[0022]
Here, the amount of the foam stabilizer added is 1.0 to 5.0 parts by weight and an excess (usually 0.5 to 1.5 parts by weight) compared to the usual latex foam production. I have. This is because the cell 14 in which gas such as air mixed with the mixed latex rubber is formed in the raw material adjusting step S1 and subsequent steps is used in order to efficiently exhibit the structural adhesive effect described above ([0010]). This is a measure to avoid phenomena such as unification. Further, as described above ([0014]), when the carboxyl-modified latex rubber 24 is used, a longer gelation time (described later ([0024])) is required as compared with the case of using only the normal latex rubber 22. However, since the occurrence of the phenomenon such as coalescence of the cells 14 increases in proportion to the gelation time, the necessity for stabilizing the generated cells 14 by increasing the amount of the bubble stabilizer is high. In this embodiment, both latex rubbers 22 and 24 constituting the main raw material are mixed in advance, and then the other auxiliary raw materials are mixed. [0020] The first mixing step S1 and the second mixing step S2 may be performed simultaneously if a sufficient shear rate can be provided.
[0023]
(About the gelling step S2)
In the gelling step S2, various inert gases such as air or nitrogen (hereinafter, referred to as air) and a gelling agent are added to the liquid raw material obtained in the raw material adjusting step S1 and mixed sufficiently. In this step, a large number of air bubbles are present in the latex foam raw material, and a gelled latex foam raw material M is obtained. The liquid raw material usually obtained in the raw material adjustment step S1 and supplied by the supply means 34a such as a pump, and the air measured and supplied by means not shown and measured by means also not shown, The process is started by sufficiently mixing the gelling agent supplied by the supply means 34b such as a pump with a mixing device 34 such as a mixing head.
[0024]
The gelling agent reduces the chemical stability of the latex rubber particles in a suspension state of particles having a diameter of about 0.5 to 5.0 μm, that is, a latex state, and agglomerates to form a so-called gelled state. In general, a liquid substance in which an aqueous solution of a fluorinated substance such as sodium silicate fluoride (SSF), potassium silicate fluoride or calcium silicate fluoride is used is used. The addition amount is preferably about 1 to 10 parts by weight based on 100 parts by weight of the liquid raw material. If this addition amount is outside the above-mentioned range, suitable gelation cannot be exhibited, that is, the liquid raw material remains forever or gelation proceeds in a short time, and it becomes difficult to form into a required shape. Such a problem occurs. Specifically, the time required for the completion of the gelation (gelation time) becomes too long or too short, so that it becomes difficult to suitably hold the cell 14 (described later ([0026])), As a result, coalescence of the cells 14 occurs, and the structural adhesive effect is not sufficiently exhibited. As the gelling agent, particularly, the above-mentioned sodium silicofluoride is preferably used because the reaction control such as the gelation start time is easy.
[0025]
The liquid material suitably gelled by the mechanism described above, that is, the gelled latex foam material M, is supplied at one end thereof onto the transfer belt 36a by the mixing head 34 under control. Actually, when the gelled latex foam raw material M is directly supplied onto the transfer belt 36a, it becomes difficult to separate the latex foam 10 obtained after heating and curing from the transfer belt 36a, or There is a fear that fine irregularities on the surface of the transfer belt 36a are transferred to the surface of the latex foam 10 and the adhesive effect is reduced. For this reason, with respect to the transfer belt 36a, the surface of the transfer belt 36a is transported in the manufacturing apparatus 30 of the gelled latex foam raw material M supplied with a predetermined thickness and heat resistance while having a high smoothness. , For example, a sheet body 37 such as a PET sheet is continuously supplied. The gelled latex foam raw material M is supplied to the sheet body 37. Further, the product thickness control means 38 converts the gelled latex foam raw material M discharged and supplied onto the transfer belt 36a into a sheet-like material 20 according to the thickness of the latex foam 10 to be obtained. Specifically, a conventionally known means such as a doctor knife or a doctor roll is employed.
[0026]
By the completion of the above-mentioned gelling, the air in the gelling raw material is held as bubbles. Since these cells become cells 14 of the finally obtained latex foam 10 as they are, the size of the cells determines the cell diameter. The bubble diameter basically depends on the gel time. In other words, if the gelation time is long, the bubbles mixed in the gelling raw material during that time come into contact with each other and coalesce or become huge, or the gelling raw material will be discharged out of the raw material. The shorter the gel time, the smaller the cell diameter can be.
[0027]
(About heating step S3)
In the heating step S3, the gelled latex foam raw material M having a required thickness is subjected to heating sufficient for the crosslinking of the raw material M to proceed sufficiently, and the crosslinking and curing reaction is advanced and completed to form the sheet-like material 20. In this embodiment, the process is performed by the tunnel heating furnace 40 capable of performing a continuous heating process. As the heating means used in the main heating step S3, in addition to the tunnel heating furnace 40, any means can be used as long as it can apply sufficient heating to the gelled latex foam raw material M so as to be crosslinked and cured. Can be adopted.
[0028]
(About final step S4)
The final step S4, which is finally performed, is a step of performing post-processing such as cutting, inspection, and the like on the obtained sheet-like material 20. Through the final step S4, a latex foam 10 as a final product is completed. Although an example of the required shape and size is described here, the product may be formed after the sheet-like material 20 is wound into a roll without any processing. Further, the manufactured latex foam 10 is protected on one side (lower side) by the sheet body 37, so that it does not inadvertently adhere during transportation or the like, but does not adhere to the other side (lower side). Since the upper side is not particularly coated, it is generally coated with a material such as a nonwoven fabric. By doing so, it is possible to avoid problems caused by storage and transfer when the latex foams 10 are stacked, and the occurrence of an adhesive effect during transfer.
[0029]
[Modification example]
In addition to the above-described embodiment, after the gelling step S2 and before the heating step S3 is performed, when the gelling raw material is in a predetermined viscosity state, for example, a conductive material for imparting conductivity may be used. Filler, magnetic substance, antibacterial substance, antibacterial / deodorant substance, deodorant substance, form stability / shape memory substance, moisture permeation suppression / waterproof substance, temperature sensitive / heat keeping / ripening / heating / absorbing substance, luminescent / fluorescent substance A third component such as a water-repellent or oil-absorbing substance is applied to impart the function of the third component, or a required release material is used on the surface of the obtained latex foam 10 to transfer and form a concavo-convex pattern. It is also possible to do so. When the concave and convex pattern is reverse-transferred by using the release material, it is possible to add a characteristic design property and to improve the coefficient of friction as a structural function of the concave and convex pattern.
[0030]
When the third component or the release material is applied to the gelled latex foam raw material M, the viscosity of the surface of the latex foam raw material M is 1 to 150 Pa · sec (1,000 to 150,000 mPa · sec). (1 Pa · sec is the viscosity immediately after the start of gelation)). If the viscosity is not in the range of 1 to 150 Pa · sec, there arises a problem that the third component does not suitably adhere to the surface of the obtained latex foam 10 and is easily peeled off.
[0031]
[Experimental example]
Hereinafter, experimental examples of various physical properties of the latex foam according to the present invention will be described. In this experiment, SBR latex rubber (trade name Nipol C-4850A; manufactured by Zeon Corporation, glass transition point -47 ° C.) as the main raw material latex rubber, and SBR-based latex rubber (trade name Nipol LX430; ZEON, glass transition point 12 ° C) were used at the ratios shown in Table 1 below, and vulcanization was performed on 100 parts by weight of both latex rubbers in accordance with the latex foam production method of the present invention. 2.0 parts by weight of a vulcanizing agent (trade name: Karuizawa Sulfur; manufactured by Karuizawa Seisakusho), 1.5 parts by weight of a vulcanization accelerator (trade name: Noxera-BZ; manufactured by Ouchi Shinko Chemical Co., Ltd.) 2.5 parts by weight of FR-14; manufactured by Kao Corporation; 2.0 parts by weight of a foam stabilizer (trade name: Trimenbase; manufactured by UNIROYAL); After adding 2.0 parts by weight of Sumilizer-BHT (manufactured by Kyodo Yakuhin) to obtain a liquid raw material, a gelling agent (trade name Keifukka Soda; manufactured by Mitsui Chemicals) is added to 100 parts by weight of the liquid raw material. Air (dry air) was added so that parts by weight and a 225 ml container would be filled with 45 g of the liquid material. Latex foams according to Examples 1 to 3 and Comparative Examples 1 and 2 were produced. This was processed into a size suitable for each physical property test, and the following physical property values (hardness (°), tensile strength (kPa), and adhesiveness (N)) were measured. The devices used in this experimental example are described below. As a reference example, an adhesive sheet manufactured from an acrylic resin was manufactured, and each physical property value was measured in the same manner.
[0032]
[Table 1]

[0033]
(Performed measurement and evaluation method)
-Hardness: Measured by ASKER F type based on JIS K6301 (hardness tester used: trade name; CL-150; manufactured by Kobunshi Keiki).
Tensile strength: A No. 1 test piece having a thickness of 3 mm was prepared from the obtained latex foam, and the test piece was pulled so that both ends of the test piece were separated from each other, and measured from the maximum load (N) at that time (use Tensile tester: trade name; AGS-5kNB; manufactured by Shimadzu Corporation).
・ Stickiness:
1. The obtained latex foam is cut into a size of 60 mm × 70 mm to obtain a test piece, and the test piece is fixed to a surface plate of a load cell using a double-sided tape or the like on the surface opposite to the measurement target surface of the test piece.
2. A 530 g, 50φ load weight attached to a chuck of a tensile tester (trade name: AGS-5kND; manufactured by Shimadzu Corporation) is placed on the upper surface of the test piece (surface to be measured) for 30 seconds.
3. The load weight that has become in an adhesive state on the measurement target surface is continuously pulled up at a pulling speed of 200 mm / min, and the load when the measurement target surface separates from the load weight is regarded as adhesive. The load of the load weight is to be subtracted from the measured load. Further, in the production method in this example, the obtained latex foam has two surfaces (a surface on the sheet body side: referred to as a first surface in the table) and the other surface (a surface on the sheet body side). In this case, the adhesiveness is measured for both of them.
[0034]
(result)
The obtained measurement results and the like are also shown in Table 1 above. From the results obtained, by setting the mixing ratio of the latex rubber as the main raw material and the carboxylated modified latex rubber in the range of 80:20 to 20:80, good adhesiveness, that is, from acrylic resin, A latex foam that exhibits at least about 90% of the tackiness of the produced pressure-sensitive adhesive sheet and that exhibits a tensile strength of about 2.5 to 4 times that of the pressure-sensitive adhesive sheet produced from the acrylic resin. Was confirmed. In particular, when the mixing ratio of the latex rubber as the main raw material and the carboxylated modified latex rubber is 50:50, the best adhesion is exhibited, and when both latex rubbers are 100%, the adhesion is extremely high. The low suggests that the balance between the structural sticking effect exhibited by achieving low hardness and the charge sticking effect exhibited by the presence of the modified latex rubber is important. Further, on the second surface, only 1/10 of the adhesiveness was exhibited as compared with the adhesiveness of the first surface, and it was confirmed that the surface smoothness of the latex foam obtained therefrom was also important. Note that formaldehyde, which is one of the environmentally hazardous substances, was not detected as a result of measurement according to JIS A 6921.
[0035]
【The invention's effect】
As described above, according to the latex foam and the method for producing the same according to the present invention, a natural or synthetic latex rubber which is a main material of the latex foam to be obtained, or a latex rubber obtained by mixing these, and a glass transition point thereof Is -30 ° C. or higher, and a latex foam raw material obtained by mixing with a carboxylated modified latex rubber is crosslinked and cured. It is possible to produce a latex foam exhibiting a high adhesion effect by having both the charge adhesion effect exhibited by the latex rubber and the structural adhesion effect of the latex foam.
[0036]
In addition, since the latex foam itself exhibits adhesiveness, it is possible to make use of the excellent mechanical strength of the latex foam itself. Can be greatly suppressed, and an effect of facilitating reuse can be achieved. Furthermore, since the production can be carried out by mixing the carboxylated modified latex rubber with the raw material to be used for the usual latex foam production, a suitable production can be carried out by a latex foam production apparatus or the like which has been conventionally used usually.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view showing a surface portion of a latex foam according to a preferred embodiment of the present invention.
FIG. 2 is a schematic diagram showing a relationship between a cell diameter and a structural adhesive effect in a latex foam according to an example.
FIG. 3 is a flowchart showing a process for producing a latex foam according to an example.
FIG. 4 is a schematic view showing an example of a latex foam manufacturing apparatus according to an example.
[Explanation of symbols]
14 cells
22 Latex rubber
24 Modified latex rubber
M Latex foam raw material

Claims (8)

A latex foam material (M) obtained by mixing at least a natural or synthetic latex rubber (22) as a main raw material, a gelling agent, a foam stabilizer, and other necessary auxiliary raw materials is crosslinked and cured. In the resulting latex foam,
A latex foam comprising a mixture of a latex rubber (22) as a main raw material and a carboxylated modified latex rubber (24) having a glass transition point of -30 ° C or higher. The latex foam according to claim 1, wherein a mixing ratio of the latex rubber (22) as the main raw material and the carboxylated modified latex rubber (24) is set in a range of 80:20 to 20:80 by weight. . 3. The latex according to claim 1, wherein the amount of the foam stabilizer is set in a range of 1.0 to 5.0 parts by weight based on 100 parts by weight of the mixture of the latex rubbers (22, 24). Form. The latex foam according to any one of claims 1 to 3, wherein the diameter of the cell (14) in the obtained latex foam (10) is set to 500 µm or less. The latex foam according to any one of claims 1 to 4, wherein a glass transition point of the latex rubber (22) constituting the main raw material is set in a range of -50 to 20 ° C. A latex rubber (22) composed of a natural or synthetic material or a mixture thereof, which is a main raw material, is mixed with a modified latex rubber (24) having a glass transition point of -30 ° C or higher and carboxylated,
To 100 parts by weight of the obtained mixed latex rubber, 1.0 to 5.0 parts by weight of a foam stabilizer and required auxiliary materials are mixed to form a liquid material,
A latex foam raw material (M) gelled by mixing 1 to 10 parts by weight of a gelling agent with 100 parts by weight of this liquid raw material is obtained.
A method for producing a latex foam, wherein the gelled latex foam raw material (M) is heated to promote crosslinking and curing. 7. The latex foam according to claim 6, wherein the mixing of the latex rubber (22) as the main raw material and the carboxylated modified latex rubber (24) is performed such that the shear rate is 10 to 10,000 min ^-1 . Production method. The method for producing a latex foam according to claim 6 or 7, wherein a fluorosilicic substance such as sodium fluorosilicate is used as the gelling agent.

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