JP2008019289A5 - - Google Patents

Description

One-pack type container sealing material and container sealing member using the same

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 seal material using 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 of heating by injecting into the groove portion at the outer peripheral end of the 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 moderate 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 also 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.

When an amine curing agent is used as the curing agent for the one-component thermosetting polyurethane elastomer, the reaction with respect to the isocyanate group is fast and uniform application is possible, but the restoration performance of the container sealing seal member which is a molded body is inferior.

JP-A-61-9481 JP 2004-75071 A JP 2002-206930 A

INDUSTRIAL APPLICABILITY The present invention provides a container sealing seal using a one-pack type polyurethane elastomer that can be applied efficiently and uniformly, has a good restoring performance of a container sealing seal member that is a molded body, and can improve the sealing performance. It is an object to provide a material and a sealing member for sealing a container using the material.

The invention of this application solves 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 % by mass , and the number average molecular weight is 2500 to 8000. aromatic isocyanate compound and a hydroxyl value of one-pack type polyurethane elastomer comprising a polyol 500~1500 (mgKOH / g), inorganic filler, and a container sealing the sealing material characterized by containing a plasticizer provide.

Secondly, the sealing material for sealing a container as described above, wherein the polyol has 4 to 5 functional groups .

3rdly, the said sealing material for container sealing whose content ratio of an inorganic filler / plasticizer is the range of 20 / 80-75 / 25 is provided.

  Fourthly, the above sealing material for sealing a container is provided in which the inorganic filler has a particle size of 0.5 to 8 μm.

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

  Sixth, the hardness formed using the container sealing material is 10-30 (JIS A hardness), the compression set is 0.1-60% (JIS 7312), and the specific gravity is 0.3- A container sealing seal member 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 the viscosity of the sealing member in the lid groove is reduced at the time of heat forming after lining the container sealing seal material to the container lid. It is possible to obtain a container-sealing seal material with little bias and excellent productivity.

  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, compression hardness and specific gravity.

  Hereinafter, the present invention will be described in detail.

  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 0.1 to 60%, preferably 1 to 40 (JIS K7312), specific gravity is 0.3 to 1.3, preferably 0.5 to 0.9.

  If the hardness is small, the sealing member may be cut when a load is applied, resulting in poor sealing. Further, when the compression set is large, the sealing member may be creep-deformed by the load caused by the decompression in the container or the 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. molecular weight is to a requirement of the invention the use of poly urethane elastomer formed of a modified polyisocyanate component and the number polyol component having an average molecular weight 500 to 1500 of 2500 to 8000.

  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 can be seen in Table 1 of Examples described later , A methyl ethyl ketone (MEK) oxime that is preferable from the viewpoint of pot life and viscosity reduction during heating is specified and used.

The invention of this application uses an aromatic isocyanate compound having an isocyanate group content of 1.0 to 3.5 % by mass and a number average molecular weight of 2500 to 8000 of a polyisocyanate component blocked with methyl ethyl ketone oxime. Is also a requirement of the invention.

  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 of more than 8000 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.

  The polyol component that reacts with an 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.

  Further, the low molecular 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 viewpoints of hardness, compression set and viscosity, which are the subject 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, those having a hydroxyl value of 500 to 1500 (mgKOH / g) as shown in Table 2 are preferable.

  When the hydroxyl value is less than 500, the polyurethane elastomer obtained is too soft and the compression set becomes too large, and when the hydroxyl value exceeds 1500, it becomes too hard and is not suitable as a sealing member.

Further, the average number of functional groups of the polyol component is preferably 2 to 12 times 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 used in a ratio of 9 to 1.5 mol, preferably about 1.00 to 1.10 mol.

  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 used for molding rubber and plastics, but in the invention of this application, inorganic fillers having a particle size of 0.5 to 8 μm are used. To improve fluidity.

  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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

In the following examples and comparative examples, the composition was appropriately adjusted according to the composition represented by the following, and a container sealing material was prepared.

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 and seal for sealing containers The material is lined on the lid of the sealed container, and then heated at 50 to 200 ° C. for 60 to 240 seconds, and the container is sealed by foaming and reacting so that the thickness of the sealed container sealing member becomes 0.1 to 10 mm. The sealing member for sealing and the lid were integrated.
<Examples 1-3, Comparative Examples 1-3>
The number average molecular weight and isocyanate group content of the TDI block polyisocyanate polymer were changed as shown in Table 1, and the physical properties of the container sealing material and the container sealing member were measured.
[viscosity]
Viscosity V20 was measured with a Brookfield rotary viscometer at a liquid temperature of 25 ° C. and 20 rpm.
[Lining workability]
Apply and apply in the groove of the rag pail canopy under the conditions of 40 ° C, nozzle diameter 2.5mm, pressure 0.1-0.4MPa, application speed 30 sheets / min. The amount was measured. A coating amount of 17 g or more was rated as ◯, and a coating amount below that as ×.
[Oven contamination]
5 g of container sealing material is put into a weighing bottle and heated at 200 ° C. for 5 minutes, and the reacted container sealing seal member is taken out from the weighing bottle. This operation is repeated 10 times, and the dirt adhering to the lid of the used weighing bottle is visually confirmed. No change was marked with ◯, and when the color changed to black, x.
[Sealing (load test)]
18g was applied in the groove | channel of the pail canopy, and the pail canopy for baking tests was produced so that hardened | cured material specific gravity might be set to 0.7. A pail can was filled with ATF (automatic fluid oil), a test pail canopy was tightened, and a 200 kg load per pail was placed upside down and stored for 3 months. After the load was released, no leakage was marked with ◯, and leakage was marked with x.

The evaluation results are shown in Table 1.

As shown in Table 1, among the polyisocyanate components blocked with methyl ethyl ketone oxime, an aromatic isocyanate compound having an isocyanate group content of 1.0 to 3.5% by mass and a number average molecular weight of 2500 to 8000 is used. By doing so, various physical properties such as viscosity and lining workability of the container sealing material and hardness and sealing property of the container sealing member were good.
<Examples 4 to 8, Comparative Examples 4 and 5>
A TDI block polyisocyanate polymer having a number average molecular weight of 4200 was used, the hydroxyl value and the number of functional groups of the polyol were changed as shown in Table 2, and the hardness of the polyurethane elastomer (JIS A hardness, 25 ° C.) was measured. Based on the measurement results, evaluation was made according to the following criteria.
Good: Hardness 15-35
Slightly hard: Hardness 36-49
Hard: Hardness 50 or more
Soft: Hardness 9 or less
Slightly soft: Hardness 10-14
The evaluation results are shown in Table 2.

As shown in Table 2, when the hydroxyl value is 500 to 1500 (mgKOH / g), the hardness of the polyurethane elastomer is appropriate, and the polyurethane elastomer is too soft and the compression set becomes too large, or conversely becomes hard. Thus, it was not unsuitable as a sealing member.
<Examples 9 to 11 and Comparative Examples 6 to 8>
The mixing ratio of MEK block polyisocyanate, crosslinking polyol, inorganic filler and plasticizer was kept constant, and the difference between the two types of inorganic filler particle size of 2 μm and 0.3 μm was compared.
[viscosity]
V20: Measured with a Brookfield rotational viscometer at a liquid temperature of 50 ° C. and 20 rpm.
[Storage stability]
It was stored at 38 ° C. for 1 month.
[Workability (bias of molded product)]
18 g of the sealing material was applied in the groove of the rag pail canopy, and the difference between the maximum and the minimum thickness of the container sealing seal member obtained by baking and curing at 175 ° C. for 4 minutes was less than 2 mm.
[Lining workability]
Apply and apply in the groove of the rag pail canopy under the conditions of 40 ° C, nozzle diameter 2.5mm, pressure 0.1-0.4MPa, application speed 30 sheets / min. The amount was measured. A coating amount of 17 g or more was rated as ◯, and a coating amount below that as ×.
[Sealing (load test)]
18g was applied in the groove | channel of the pail canopy, and the pail canopy for baking tests was produced so that hardened | cured material specific gravity might be set to 0.7. A pail can was filled with ATF (automatic fluid oil), a test pail canopy was tightened, and a 200 kg load per pail was placed upside down and stored for 3 months. After the load was released, no leakage was marked with ◯, and leakage was marked with x.
[Sealing (pressure resistance test)]
The internal pressure was held at 0.1 MPa × 10 minutes and the leakage was evaluated as “x” and the case where no leakage occurred.

  The evaluation results are shown in Table 3.

  As shown in Table 3, when an inorganic filler having a particle size of 0.3 μm is used, the viscosity is remarkably high, and this high viscosity cannot be uniformly injected during lining in the lid groove. It is considered that the sealing performance after molding is greatly affected.

  In addition, when an inorganic filler having a particle size exceeding 8 μm is used, it causes sedimentation during storage, so 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.

  According to 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 at the time of thermoforming after sealing the container sealing material to the container lid. In addition, it is possible to obtain a container sealing seal material that is free from oven contamination and excellent in productivity.

Claims (6)

An isocyanate group whose isocyanate group is blocked with methyl ethyl ketone oxime is 1.0 to 3.5 % by mass , an aromatic isocyanate compound having a number average molecular weight of 2500 to 8000, and a hydroxyl value of 500 to 1500 (mgKOH / g). one-pack type polyurethane elastomer comprising a polyol, an inorganic filler, and a container sealing the sealing material characterized by containing a plasticizer. 2. The container sealing material according to claim 1, wherein the polyol has 4 to 5 functional groups . 3. The container sealing material according to claim 1, wherein the content ratio of the inorganic filler / plasticizer is in the range of 20/80 to 75/25.   The container sealing material according to any one of claims 1 to 3, wherein the inorganic filler has a particle size of 0.5 to 8 µm. The container sealing material according to any one of claims 1 to 4, which contains bismuth tris (2-ethylhexanoate) 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.