JP4979223B2 - Sealing composition for lid - Google Patents

Description

  The present invention relates to a lid sealant composition, and more particularly, to a lid sealant composition that is less liable to flow due to a decrease in viscosity within a lid when it is thermoformed after application to a container lid.

  Conventionally, a manufacturing method of a lid with a sealing material is a method of cutting a sealing material molded product that has been molded in advance into an appropriate shape and fitting it into the lid, and injecting a liquid polymer compound into the premises of the outer periphery of the lid, Two methods are used: a method of forming a sealant molding by heat curing.

  Foamed vulcanized rubber is used for the method of cutting the molding material molded in advance into a suitable shape and fitting it into the lid, which provides high sealing performance, but before the sealing material is attached to the lid Many processes are required, work efficiency is low, and cost is high. On the other hand, the method of forming a sealing material molding by injecting a liquid polymer compound into the premises of the outer peripheral edge of the lid and heat-curing can provide high productivity with a relatively simple device, This method is used for many lids with a sealing material.

  In general, polyvinyl plastisol has been used as a method of injecting and curing a liquid polymer compound into the premises at the outer peripheral end of the lid from the viewpoints of workability, ease of moldability, cost, and the like. However, in recent years, the generation of dioxins during disposal due to the burning of polyvinyl chloride has become a social problem, and depolyvinyl chloride has been studied. Polyvinyl chloride plastisols are unsuitable for solvent-based contents, and their sealing properties tend to be slightly inferior to rubber-based sealants.

  Molded products made of polyurethane resin compositions have high tensile strength, fatigue resistance, good low-temperature flexibility, and wear resistance, so they are widely used as materials for rolls, packings, and various machine parts. ing. Because of these characteristics, a polyurethane resin composition has been proposed as a container lid sealing composition for the purpose of depolyvinyl chloride.

As an example of using a polyurethane resin as a container lid sealing material such as a pail can or an open drum, there is a technique described in JP-A-61-9481. (Patent Document 1)
This technique consists of a first liquid mainly composed of a polyurethane prepolymer and a second liquid mainly composed of a polyol. When the two liquids are mixed, the viscosity of the mixture in a temperature range of 0 to 60 ° C. Is adjusted to 200 to 20000 mPa · s.

  In such a casting operation using two liquids, a tank for storing the main component and a tank for storing the hardener component are prepared and sent from each tank to the mixing device with a metering pump so that a constant mixing ratio is obtained. Liquid. After mixing the two liquids by mechanical stirring or high-pressure collision method, they are poured into a mold and heat-treated for a certain period of time to obtain an elastomer molded product.

  In the case of a two-part composition as described in JP-A-61-9481, the heat-cured molded product has excellent physical properties such as tensile strength, fatigue resistance, and good low-temperature flexibility. However, it took a long time to complete curing and was unsuitable for mass production systems. In addition, since there is a problem that viscosity increase in the two-component mixer and constant discharge are difficult and work efficiency is poor, there is a limit to shortening the curing time. Furthermore, when switching from a one-pack type such as a plastisol of polyvinyl chloride to a two-pack type, new equipment such as a two-pack quantitative feeding device and a short-time stirring mixer is required.

  In order to solve the problems of these two-component compositions, there is a technique described in JP-A-2002-206930. (Patent Document 2) In this technique, a one-component thermosetting polyurethane resin using a blocked isocyanate is introduced. Since it is a one-component type, the problem that it is difficult to shorten the curing time of the two-component composition is solved, and a new device such as a two-component quantitative liquid feeding device and a short-time stirring mixer is not required, Conventional injection devices for polyvinyl chloride plastisol can be used.

JP-A-61-9481 JP 2002-206930 A

  However, even in the technique described in Japanese Patent Application Laid-Open No. 2002-206930, when the one-component thermosetting polyurethane resin composition is poured into the premises at the outer peripheral end of the lid and cured, the polyurethane resin composition is heated by heating. The viscosity of the polyurethane resin composition is extremely lowered, and the polyurethane resin composition flows due to a slight inclination of the belt conveyor that conveys the lid in the heating device and is unevenly distributed in the lid structure, so that the thickness of the cured molded product is not uniform (hereinafter, This is referred to as uneven thickness).

  Accordingly, the object of the present invention is to inject the composition for the lid sealing material into the premises at the outer peripheral end of the lid and cure it, without causing the viscosity of the composition for the lid sealing material to be extremely reduced by heating, An object of the present invention is to provide a one-component thermosetting polyurethane resin lid sealing material composition having a uniform thickness of a cured molded article and excellent sealing properties.

In order to achieve the above object, the present invention has found that the above-mentioned problems can be solved by the addition of a viscosity reduction inhibitor, and has been completed. The composition for lid sealing material of the invention of claim 1 of the present application comprises the following components (A), (B) and (C), and (A) per 100 parts by weight of a blocked polyisocyanate in which an isocyanate group is blocked, (C) It is a liquid or pace-like composition for lid sealing materials characterized by containing 40 to 70 parts by weight of an anti-viscosity agent having an average particle size of 0.1 to 10.0 μm.
(A) Block polyisocyanate in which isocyanate group is blocked (B) Active hydrogen group-containing compound (C) Viscosity reduction inhibitor having an average particle diameter of 0.1 to 10.0 μm.
In addition, the invention of claim 2 of the present application is to change the rotational viscosity (20 rpm) from the start of heating until the start of thickening by reaction, by heating the composition for lid sealing material to increase the liquid temperature. The composition for a lid sealing material according to claim 1, wherein the composition has a viscosity of 600 mPa · s or more when it is most lowered.

  Examples of the polyisocyanate constituting the blocked isocyanate component used in the present invention include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, and modified products thereof. These can be used alone or in admixture of two or more.

  Further, it is more preferable to use an isocyanate group-terminated prepolymer obtained by reacting these organic isocyanates with an active hydrogen group-containing compound.

  The active hydrogen-containing compound used for the synthesis of the isocyanate group-terminated prepolymer is a component constituting a normal polyurethane resin, and adipate, lactone, carbonate, and ether polyols can be used depending on the application.

  Examples of the blocking agent used for blocking the isocyanate group include ε-caprolactam, methyl ethyl ketone oxime, and ethyl acetoacetate.

  Examples of the active hydrogen group-containing compound (B) of the present invention include high molecular polyols, low molecular polyols, polyamines, amino alcohols, hydrazides and the like. These can be used alone or in combination of two or more.

  Examples of the (C) viscosity reduction inhibitor used in the present invention include calcium carbonate, barium sulfate, titanium oxide, clay, and talc. These can be used alone or in combination of two or more. The average particle size of the viscosity reduction inhibitor is preferably 0.1 to 10.0 μm. When the average particle size is 0.1 μm or less, the viscosity becomes high, and a sufficient coating amount cannot be discharged at the time of continuous lining in the lid structure. If the average particle size is 10.0 μm or more, the viscosity will be low, and uneven thickness will occur during heat curing. On the other hand, when the viscosity is low, the viscosity reduction preventive agent precipitates with time, the composition for the lid sealant becomes non-uniform, and sufficient sealability cannot be maintained. The blending amount of this viscosity reduction inhibitor is (A) 40 to 70 parts by weight, preferably 42 to 68 parts by weight, more preferably 50 to 60 parts by weight per 100 parts by weight of the blocked polyisocyanate in which the isocyanate group is blocked. It is good to let them. If the viscosity reduction inhibitor is 40 parts by weight or less, the viscosity will be low, resulting in uneven thickness during heat curing. When the viscosity reduction preventing agent is 70 parts by weight or more, the viscosity increases, and a sufficient amount of coating cannot be discharged during continuous running into the lid.

  The composition for lid sealing materials of the present invention can be used in combination with various known additives as required. Additives include plasticizers, foaming agents, catalysts, dyes, pigments, lubricants, reinforcing agents, flame retardants, antioxidants, UV absorbers, light stabilizers, electrical insulation improvers, fungicides, etc. Can be mentioned.

  As described above in detail, according to the present invention, a composition for a lid sealing material can be provided which, after being applied to a lid, has a small decrease in viscosity at the time of thermoforming, little uneven thickness, and good sealing properties for a long period of time.

  Hereinafter, the present invention will be described in more detail with reference to examples.

The raw materials used are shown below.
Block polyisocyanate: methyl ethyl ketone oxime Block isocyanate active hydrogen group-containing compound: dodecanedioic acid dihydrazide
N-12, Nippon Hydrazine Kogyo Co., Ltd. viscosity reduction inhibitor c1: calcium carbonate, average particle size 1.25 μm
Whiteon SSB, Shiraishi Calcium Co., Ltd. Viscosity Reduction Inhibitor c2: Calcium carbonate, Average particle size 0.05 μm
Shiraka Hana AA, Shiraishi Calcium Co., Ltd. Viscosity Reduction Inhibitor c3: Calcium Carbonate, Average Particle Size 14.8 μm
NN # 200, plasticizer manufactured by Nitto Flour & Chemical Co., Ltd .: epoxidized soybean oil, O-130P, foaming agent manufactured by Asahi Denka Co., Ltd .: ADCA foaming agent, uniform AZ-L, manufactured by Otsuka Chemical Co., Ltd.

  Example 1 After mixing 100 parts by weight of a block polyisocyanate and 7 parts by weight of an active hydrogen group-containing compound, 30 parts by weight of a plasticizer, 50 parts by weight of a viscosity reduction inhibitor c1, and 4 parts by weight of a foaming agent were added to make it uniform. And then defoamed to prepare a composition for a lid sealant. The viscosity of this composition at a liquid temperature of 50 ° C. and 20 rpm was measured with a Brookfield rotational viscometer. The viscosity at a liquid temperature of 50 ° C. and 20 rpm is preferably 10,000 mPa · s or less. Furthermore, this composition was heated, the continuous viscosity until the start of thickening by reaction was measured, and the minimum viscosity until the start of thickening was investigated. The minimum viscosity until the start of thickening is 600 mPa · s or more. Next, this composition was applied to the rug pail canopy premises using a discharge machine under conditions of a liquid temperature of 40 ° C., a nozzle diameter of 2.5 mm, a pressure of 0.1 to 0.4 MPa, and a coating speed of 30 sheets / minute. Was measured. A coating amount of 17 g or more can be kept good. Next, 17 g of this composition was poured into the premises of the rag pail canopy using a dispenser, heated at 170 ° C. for 3 minutes, foamed and cured in the oven used to produce the pail canopy, and the thickness of the molded packing was measured. did. A difference between the maximum thickness and the minimum thickness in the packing per pail canopy is less than 2 mm. Similarly, 17 g of this composition was poured into the premises of the rag pail canopy using a discharger, heated at 170 ° C. for 3 minutes, foamed, and cured to prepare a test sample canopy having a packing. A pail can was filled with 5 liters of an automatic liquid for automobiles (Idemitsu Pro ATF), and the sample canopy was caulked with a fastening machine to prepare a test pail can. A test pail can is placed upside down on a horizontal pallet, and a load is applied on top of the test pail can at 200 kg / can. After storage at room temperature for 3 months, the load was removed, the pail can was laid down and allowed to stand for 2 hours, and leakage of the automatic liquid for automobiles was confirmed visually. Make no leakage. These results are shown in Table 1.

  Example 2 After mixing 100 parts by weight of a block polyisocyanate and 7 parts by weight of an active hydrogen group-containing compound, 30 parts by weight of a plasticizer, 40 parts by weight of a viscosity reduction inhibitor c1 and 4 parts by weight of a foaming agent were added and uniform. And then defoamed to prepare a composition for a lid sealant. Hereinafter, the same test as in Example 1 was performed. These results are shown in Table 1.

  Example 3 After mixing 100 parts by weight of a block polyisocyanate and 7 parts by weight of an active hydrogen group-containing compound, 30 parts by weight of a plasticizer, 70 parts by weight of a viscosity reduction inhibitor c1 and 4 parts by weight of a foaming agent were added and uniform. And then defoamed to prepare a composition for a lid sealant. Hereinafter, the same test as in Example 1 was performed. These results are shown in Table 1.

  Comparative Example 1 After mixing 100 parts by weight of a block polyisocyanate and 7 parts by weight of an active hydrogen group-containing compound, 30 parts by weight of a plasticizer, 30 parts by weight of a viscosity reduction inhibitor c1, and 4 parts by weight of a foaming agent were added and uniform. After mixing, a defoaming and lid sealant composition was prepared. Hereinafter, the same test as in Example 1 was performed. These results are shown in Table 1.

  Comparative Example 2 After mixing 100 parts by weight of a block polyisocyanate and 7 parts by weight of an active hydrogen group-containing compound, 30 parts by weight of a plasticizer, 80 parts by weight of a viscosity reduction inhibitor c1, and 4 parts by weight of a foaming agent were added and uniform. After mixing, a defoaming and lid sealant composition was prepared. Hereinafter, the same test as in Example 1 was performed. These results are shown in Table 1.

  Comparative Example 3 After mixing 100 parts by weight of block polyisocyanate and 7 parts by weight of active hydrogen group-containing compound, 30 parts by weight of plasticizer, 50 parts by weight of viscosity reduction inhibitor c2 and 4 parts by weight of foaming agent were added and uniform. After mixing, a defoaming and lid sealant composition was prepared. Hereinafter, the same test as in Example 1 was performed. These results are shown in Table 1.

  Comparative Example 4 After mixing 100 parts by weight of a block polyisocyanate and 7 parts by weight of an active hydrogen group-containing compound, 30 parts by weight of a plasticizer, 50 parts by weight of a viscosity reduction inhibitor c3, and 4 parts by weight of a foaming agent were added uniformly. After mixing, a defoaming and lid sealant composition was prepared. Hereinafter, the same test as in Example 1 was performed. These results are shown in Table 1.

Claims (2)

(A) Block polyisocyanate in which isocyanate group is blocked (B) Active hydrogen group-containing compound (C) Consisting of at least one selected from calcium carbonate, barium sulfate, titanium oxide, clay, and talc, average particle size of 0.1 Viscosity reduction inhibitor of ˜10.0 μm (C) Average particle size 0 per 100 parts by weight of the polyisocyanate comprising the above components (A), (B) and (C) and having blocked isocyanate groups (A) A liquid or paste-like composition for lid sealing material, comprising 40 to 70 parts by weight of a viscosity reduction inhibitor having a viscosity of 1 to 10.0 μm.   The composition for lid sealant is heated to increase the liquid temperature, and the viscosity at the time of the decrease is 600 mPa · s due to the change in rotational viscosity (20 rpm) from the start of heating to the start of thickening by reaction. It is the above, The composition for lid sealing materials of Claim 1 characterized by the above-mentioned.