JP2008019289A - One-pack type container sealing material and container sealing seal member using the same - Google Patents

Abstract

[PROBLEMS] To be excellent in safety, environmental performance, sealing performance, durability and the like, and less in the bias due to a decrease in the viscosity of the sealing member in the lid groove at the time of heat forming after sealing the sealing member to the container lid, and excellent in productivity. Provide a sealing material for container sealing.
An aromatic isocyanate compound having a isocyanate group content of 1.0 to 3.5 wt% and a number average molecular weight of 2500 to 8000 and a hydroxyl value as a sealing material for sealing a container. Is a mixture of a one-component polyurethane elastomer and an inorganic filler / plasticizer composed of a polyol of 500-1500 (mgKOH / g).
[Selection figure] None

Description

  The invention of this application relates to a container-sealing seal material and a container-sealing seal member that are excellent in sealing performance and have low environmental load and high work efficiency. More specifically, the invention of this application relates to a container sealing material made of a one-component polyurethane elastomer suitable for a sealed container and a container sealing seal member using the same.

  Generally, a sealing member such as a gasket is provided between the opening of the container and the lid in order to improve the sealing performance of the container. The sealing member used at this time is a type in which foamed vulcanized rubber cut into the same shape as the groove shape at the outer peripheral end of the lid is fitted into the lid, or a liquid sealing material made of plastisol such as vinyl chloride. A type in which heat is injected into the groove at the outer peripheral end is widely used. However, the type in which the foamed vulcanized rubber is fitted has a problem that many processes and costs are required until the sealing member is attached to the groove portion of the lid, resulting in poor work efficiency and high cost. On the other hand, the method of injecting vinyl chloride plastisol into the groove at the outer peripheral end of the lid and heat-curing is a simple device and has good working efficiency, so this method is currently used for many sealing members. .

However, vinyl chloride is not only a substance that causes dioxins, which has become a problem in recent years, but a large amount of plasticizers harmful to the human body, such as dioctyl phthalate, is used for its processing. Moreover, when the plastisol of polyvinyl chloride comes into contact with oil-based contents such as automatic fluid oil (lubricating oil), the plasticizer in the plastisol of polyvinyl chloride is extracted into the oil and thins, and the surface hardness becomes hard and the sealing performance There is a problem that the content drops significantly and the contents leak. In order to solve these problems, there is a method using a polyurethane elastomer having appropriate elasticity and excellent mechanical strength and wear resistance. In this method using a polyurethane elastomer, a liquid composition comprising a polyisocyanate component and a polyol component is lined in a sealable container, and this is heated and baked to integrally form a polyurethane elastomer sealing member in the sealable container. is there. For example, a method using a polyurethane elastomer as a sealing member of a sealed container such as a pail can or an open drum (Patent Document 1) is known. This method mainly uses a first liquid mainly composed of a polyurethane prepolymer and a polyol. It is comprised from the 2nd liquid used as a component. Then, the two components, the tank containing the main component and the tank containing the hardener component, are fed to the mixing device using a metering pump so that the mixing ratio is constant, and the two components are mixed and poured into a mold. An elastomer molded product is obtained by heat treatment for a certain time. This method is a two-component improvement method in which the problem that the viscosity of the two-component sealing member composition is once reduced and biased during thermoforming is prevented by adding a thickener component (Patent Document 2). . However, in the case of such a two-component composition, the existing simple equipment such as that used for polyvinyl chloride plastisol cannot be used, and therefore, an expensive mixing system must be newly purchased. There is. Various methods have been devised to solve the two-pack type problem. For example, there is a method of using a one-component thermosetting polyurethane elastomer using a blocked isocyanate (Patent Document 3). Since this improved method is a one-component type, it does not require a new device such as a two-component fixed-quantity liquid feeding device or a mixer for short-time stirring, and the existing equipment using polyvinyl chloride plastisol can be used as it is. However, in this method, when the one-component thermosetting polyurethane elastomer material is injected into the groove at the outer peripheral end of the lid and cured, the viscosity of the polyurethane resin composition is extremely lowered by heating. There is a problem that the polyurethane resin composition flows due to a slight inclination of the belt conveyor to be conveyed and is biased in the lid groove, resulting in non-uniform thickness of the cured molded product, resulting in poor sealing.
: JP-A-61-9481 : JP-A-2004-75071 : JP 2002-206930 A

  Efficiently using a polyol with a high sealing performance as a curing agent instead of an amine curing agent, which has a fast reaction to isocyanate groups and can be uniformly applied, but is considered to be inferior in the restoration performance of the container sealing seal member. Provided are a container sealing seal material made of a one-pack type polyurethane elastomer that is not only uniformly applied but also has a good restoration performance of a container sealing seal member that is a molded body, and a container sealing seal member that is excellent in sealing performance.

  The invention of this application is to solve the above-mentioned problems. First, the isocyanate group content in which the isocyanate group is blocked with methyl ethyl ketone oxime is 1.0 to 3.5 wt%, and the number average molecular weight is 2500 to 8000. Provided is a container sealing material containing a mixture of a one-component polyurethane elastomer composed of an aromatic isocyanate compound and a polyol having a hydroxyl value of 500 to 1500 (mgKOH / g) and an inorganic filler / plasticizer.

  Secondly, the above-mentioned container sealing material using a polyurethane elastomer which is a reaction product using a polyol having functional groups 4 to 5 is provided.

  Third, the container sealing material is provided with an inorganic filler / plasticizer mixing ratio in the range of 20/80 to 75/25.

  Fourth, the container sealing material is provided with the inorganic filler having a particle diameter of 0.5 to 8 μm.

  Fifth, the above-described container sealing material using bismuth tris (2-ethylhexanoate) as a catalyst is provided.

  Sixth, the hardness formed using the container sealing material is 10 to 30 (JIS A hardness), the compression set is 0.1 to 60% (JIS 7312), and the specific gravity is 0.3 to 0.3. A container-sealing seal member that is 1.3 is provided.

  According to the first aspect of the present invention, it is excellent in safety, environmental performance, sealing performance, durability, and the like, and is less biased due to a decrease in the viscosity of the sealing member in the lid groove when the sealing member is lined to the container lid during thermoforming. A container sealing material with excellent productivity can be obtained.

  According to the second aspect of the invention, in addition to the above effects, a polyurethane elastomer suitable as a sealing material can be obtained.

  According to the third aspect of the invention, it is possible to specify a mixing ratio of an inorganic filler and a plasticizer suitable as a container sealing material.

  According to the fourth aspect of the invention, it is possible to specify a viscosity range suitable as a container sealing material.

  According to the fifth aspect of the present invention, it is possible to obtain a container-sealing seal material that has little contamination and good reaction rate.

  According to the sixth aspect of the invention, it is possible to obtain a container-sealing seal member that has excellent hermeticity, such as hardness, compression set, and specific gravity.

  The sealed container filled with the contents is not necessarily managed in a temperature-controlled room, and is required to exhibit excellent physical properties such as sealing performance, opening performance, and durability under severe conditions. For example, a sealing member for a pail canopy widely known as a sealed container has a hardness of 5 to 40, preferably 10 to 30 (JIS A hardness), and a compression set of 0 to 60%, preferably 1 to 40 ( JIS K7312), specific gravity is 0.3 to 1.3, preferably 0.5 to 0.9 is a suitable range. If the hardness is small, the sealing member may be cut when a load is applied, resulting in poor sealing. Further, when the permanent compression strain is large, the sealing member may be creep-deformed by a load caused by decompression in the container or stacking of the containers, and may leak as soon as the load on the container is removed. Further, when the specific gravity is smaller than the above range, the elasticity as the sealing member may be impaired. On the other hand, when the specific gravity is larger than the above range, the flexibility is insufficient.

  The invention of this application is to supply a sealing member for sealing a container that satisfies the above physical properties and can be used as it is in an existing lining apparatus used in a conventional method using polyvinyl chloride plastisol. It is a requirement of the invention to use a urethane elastomer composed of a modified polyisocyanate component having a molecular weight of 2500 to 8000 and a polyol component having a number average molecular weight of 500 to 1500. As the isocyanate constituting the polyisocyanate component in the invention of this application, a polyisocyanate component obtained by modifying an aromatic isocyanate is specified and used. Tolylene diisocyanate (TDI) is particularly used from the viewpoint of viscosity reduction during heating. A system is preferred. Aromatic polyisocyanates can be obtained by dimerization reaction, trimerization reaction, high polymerization reaction of aromatic isocyanates, and urethanization reaction of these isocyanate reactants and polyfunctional active hydrogen group-containing compounds. The polyisocyanate compound used in the invention of the application uses a polyisocyanate component blocked with methyl ethyl ketone (MEK) oxime.

  As an isocyanate group blocking agent, ε-caprolactam, methyl ethyl ketone oxime, ethyl acetoacetate, active methylene, butyl alcohol and the like are generally known. In the invention of this application, as shown in Table 1, pot life and heating Methyl ethyl ketone (MEK) oxime, which is preferable from the viewpoint of lowering the viscosity, is specified and used. The invention of this application also uses an aromatic isocyanate compound having a polyisocyanate component blocked with methyl ethyl ketone oxime having an isocyanate group content of 1.0 to 3.5 wt% and a number average molecular weight of 2500 to 8000. It is a requirement of the invention.

  The reason for using an aromatic isocyanate compound having an isocyanate group content of 1.0 to 3.5 wt% and a number average molecular weight of 2500 to 8000 among the polyisocyanate components blocked with methyl ethyl ketone oxime in the invention of this application is as follows. As is clear from Table 1, if the number average molecular weight is less than 2500, the viscosity becomes too high and uniform coating becomes difficult, and the molded body has high hardness and poor sealing performance. On the other hand, those having a number average molecular weight exceeding 8500 are not only difficult to handle due to their too high viscosity, but also the molded product has low hardness and poor sealing performance for a sealing container.

イソシナネート基と反応するポリオール成分としては、大きく分けて低分子ポリオールと高分子ポリオールに分類できる。高分子ポリオールは数平均分子量が５００以上のポリオールであり、例えば、ポリプロピレングリコール系ポリエーテルポリオール（ＰＰＧ）、ポリテトラメチレンエーテルグリコール（ＰＴＭＧ）、アジペート系ポリエステルポリオール、ポリカプロラクトン系ポリエステスポリオール、ポリカーボネート系ポリオール等が例示される。また、低分子ポリオールは、数平均分子量５００未満のポリオールであり、例えばエチレングリコール、１，２−プロパンジオール、１，３−プロパンジオール、１，２-ブタンジオール、１，３−ブタンジオール、１，４−ブタンジオール、１，５−ペンタンジオール、１，６−ヘキサンジオール、３−メチル−１，５−ペンタンジオール、ペンチルグリコール、１，８−オクタンジオール、１，９−ノナンジオール、ジエチレングリコール、シクロヘキサン−１，４−ジオール、ジクロヘキサン−１，４ジメタノール、ジメチロールヘプタン、ダイマー酸ジオール、トリメチロールプロパン、グリセリン、ジグリセリン、トリグリセリン、ヘキサントリオール、クオドロール等が例示される。

The polyol component that reacts with the isocyanate group can be roughly classified into a low molecular polyol and a high molecular polyol. The polymer polyol is a polyol having a number average molecular weight of 500 or more. For example, polypropylene glycol-based polyether polyol (PPG), polytetramethylene ether glycol (PTMG), adipate-based polyester polyol, polycaprolactone-based polyester polyol, polycarbonate-based Examples include polyols. The low molecular weight polyol is a polyol having a number average molecular weight of less than 500, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, , 4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, pentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, Examples include cyclohexane-1,4-diol, dichlorohexane-1,4 dimethanol, dimethylol heptane, dimer acid diol, trimethylolpropane, glycerin, diglycerin, triglycerin, hexanetriol, and quadrol.

  A low molecular weight polyol is desirable from the viewpoint of the hardness, permanent compression strain, and viscosity, which are the problems of the invention of this application, and a tri- to 10-mer of diglycerin and glycerin is particularly preferred. As a polyol component suitably used in the invention of this application, a hydroxyl value as shown in Table 2 is preferably 500 to 1500 (mgKOH / g). When the hydroxyl group is less than 500, the obtained polyurethane elastomer is too soft and the compression set becomes too large, and when it exceeds 1500, the polyurethane elastomer becomes too hard and is not suitable as a sealing member. Furthermore, the average number of functional groups of the polyol component is preferably 2 to 12 with respect to the average number of functional groups of the polyisocyanate component since it is desirable that an appropriate amount of a crosslinked structure is introduced into the polyurethane elastomer.

  In the invention of this application, when a polyurethane elastomer is synthesized by reacting a polyisocyanate component and a polyol component, the number of moles of isocyanate groups per mole of active hydrogen atoms in the polyisocyanate component is 0.00. It is preferably used in a ratio of 9 to 1.5 mol, preferably about 1.00 to 1.10 mol.

この出願の発明の容器密封用シール素材はＭＥＫでブロックされたポリウレタンエラストマーとそれ自体は公知の発泡剤、触媒、染料、顔料、滑剤、補強剤、難燃向上剤、酸化防止剤、紫外線吸収剤、光安定剤、電気絶縁性向上剤、防カビ剤等を混合するものであるが、この出願の発明の特徴は上記添加剤の形状や組成を特定することにより容器密封用シール素材としての効果を向上するものである。例えば、可塑剤や充填剤はゴムやプラスチックスの成形時に使用するものと同じ可塑剤や充填剤を用いるが、この出願の発明では無機充填材は粒径が０．５〜８μｍのものを使用することにより流動性を向上させる。

The container sealing material of the invention of this application is a polyurethane elastomer blocked with MEK and per se known foaming agents, catalysts, dyes, pigments, lubricants, reinforcing agents, flame retardants, antioxidants, UV absorbers , Light stabilizers, electrical insulation improvers, antifungal agents, etc., but the invention features the application as a sealing material for container sealing by specifying the shape and composition of the additive. Is to improve. For example, plasticizers and fillers are the same plasticizers and fillers that are used when molding rubber and plastics. In the invention of this application, inorganic fillers having a particle size of 0.5 to 8 μm are used. To improve fluidity.

  For example, Table 3 compares the difference between two types of MEK block polyisocyanate, cross-linking polyol, inorganic filler, and plasticizer with the same mixing ratio of inorganic filler and particle size of 2 μm and 0.3 μm. However, when the particle size of the inorganic filler is 0.3 μm, the viscosity is remarkably high, and this high viscosity causes the uniform injection during lining in the lid groove and seals after molding. It is thought that it greatly affects the sex. In addition, since it will cause sedimentation separation at the time of storage when the particle size of the inorganic filler exceeds 8 μm, the particle size of the inorganic filler in the invention of this application is in the range of 0.5 to 8 μm. Is preferred.

  Although not described in Table 3, a suitable mixture of an inorganic filler and a plasticizer when using an inorganic filler having a particle size of 0.5 to 8 μm as judged from a sealing member for container sealing and molding efficiency The ratio was also found to be in the range of 20/80 to 75/25 inorganic filler / plasticizer.

反応触媒としては、ジブチルチンジラウレート、ジオクチルチンジラウレート(ＤＯＴＤＬ)、トリエチルアミン、ビスマストリス（２−エチルヘキサノエート）、ジアザビシクロウンデセン、ジメチル錫ビス（イソオクチルグリコレート）、モノメチル錫トリス（イソオクチルグリコレート）、ジ（ｎ−オクチル）錫Ｓ,Ｓ‘−ビスイソオクチルメルカプトアセテート、ジ(n−オクチル)錫マレートポリマー等が挙げられるが、ポットライフ、反応速度、汚染性の点からビスマストリス（２−エチルヘキサノエート）が特に好ましい。

Reaction catalysts include dibutyltin dilaurate, dioctyltin dilaurate (DOTDL), triethylamine, bismuth tris (2-ethylhexanoate), diazabicycloundecene, dimethyltin bis (isooctyl glycolate), monomethyltin tris (iso Octyl glycolate), di (n-octyl) tin S, S′-bisisooctyl mercaptoacetate, di (n-octyl) tin malate polymer, etc., from the viewpoint of pot life, reaction rate, and contamination Bismuth tris (2-ethylhexanoate) is particularly preferred.

  As the antioxidant, hindered phenol-based antioxidants are preferable. Specifically, 3-methyl-2,6-tert-butyl-phenol, tetrakis [methylene-3 (3 ', 5'-di- -Tert-butyl-4'-hydroxyphenyl) propionate] methane can be exemplified as the most preferred antioxidant.

  A container sealing material having the following composition is lined on the lid of the sealed container. Next, heating is performed at 150 to 200 ° C. for 60 to 240 seconds, and the sealing member and the lid are integrated by foaming and reacting so that the molded sealing member has a thickness of 0.1 to 10 mm.

TDI block polyisocyanate polymer
Number average molecular weight = 4200
Number of latent isocyanate functional groups = 2
Latent isocyanate content = 2%
Polyol: molecular weight 168, hydroxyl value 1335
Plasticizer: Epoxidized soybean oil Filler: Calcium carbonate Average particle size 2.0 μm
Foaming agent: Azodicarbonamide (ADCA)
Reaction catalyst: bismuth tris (2-ethylhexanoate)
Antioxidants: 3-methyl-2,6-tert-butyl-phenol, tetrakis [methylene-3 (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane

Claims (6)

  An aromatic isocyanate compound having an isocyanate group blocked with methyl ethyl ketone oxime and having a number average molecular weight of 2500 to 8000 and a hydroxyl value of 500 to 1500 (mgKOH / g) A container-sealing seal material comprising a mixture of a one-component polyurethane elastomer and an inorganic filler / plasticizer.   2. The sealing material for container sealing according to claim 1, wherein a polyurethane elastomer which is a reactive organism using a polyol having functional groups 4 to 5 is used.   3. The container sealing material according to claim 1, wherein the mixing ratio of the inorganic filler / plasticizer is in the range of 20/80 to 75/25.   The container sealing material according to claim 1, wherein the inorganic filler has a particle size of 0.5 to 8 μm.   The sealing material for container sealing according to claim 1, wherein bismuth tris (2-ethylhexanoate) is used as a catalyst. Hardness molded using the sealing material for container sealing according to any one of claims 1 to 5 (JIS A hardness), compression set 0.1 to 60% (JIS 7312), and specific gravity 0. The sealing member for container sealing which is 3-1.3.