JP5398490B2 - Metal cap manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a metal cap, and more particularly, to a method for producing a metal cap on which a liner material having excellent openability after aging is formed.

As a metal cap liner material, polyurethane elastomer is suitably used because it has excellent flexibility and resilience as a sealing material, can exhibit excellent sealing properties, and is excellent in safety and hygiene. (Patent Document 1).
In general, polyurethane elastomers used for liner materials are blended with additives such as lubricants, thickeners, antioxidants, pigments, etc. However, polyurethane elastomers are inferior in slipperiness, and in particular twist-off. When used for a cap of a type that opens and closes by turning, such as a cap or a screw cap, it is essential to add a lubricant in order to ensure openability.
As the lubricant blended in the polyurethane elastomer, an amide (amide) -based or silicone-based lubricant that is excellent in safety and can be used as a liner material for a cap for food is suitably used. Generally, it is blended and used in a polyol compound constituting a polyurethane elastomer (Patent Document 2).

JP 2003-205963 A JP 2008-179746 A

  When fatty acid amide is used as a lubricant, the fatty acid amide oozes out on the surface of the liner material made of polyurethane elastomer and improves the lubricity of the liner material. In the heat sterilization process exceeding the melting point of the fatty acid amide, When the fatty acid amide on the liner surface melts again and re-dissolves in the liner, the slipperiness of the surface is lost, and the container to which the metal cap with such liner material is applied is used for a long time. When stored, the contact surface between the liner material and the container mouth part is pseudo-adhered, which makes it difficult to open the cap.

  Accordingly, an object of the present invention is to provide a metal cap using a liner material made of a polyurethane elastomer in which a fatty acid amide is blended as a lubricant, so that the opening performance does not deteriorate even when stored for a long time. It is providing the manufacturing method of the metal cap which has an excellent liner material.

  According to the present invention, in the method for producing a metal cap in which a polyurethane elastomer composition is applied to the inner surface of a metal cap shell and this is heated and cured to form a liner material, the polyurethane elastomer composition comprises a fatty acid amide, a clay. A two-component polyurethane elastomer comprising a polyol component and a polyisocyanate component containing a mineral filler and silicone, and a composite comprising a fatty acid amide, a clay mineral filler and silicone in a polyurethane elastomer composition applied to the metal cap Provided is a method for producing a metal cap characterized in that the body is produced and dispersed.

In the manufacturing method of the metal cap of the present invention,
1. The temperature of the polyurethane elastomer composition containing the composite is controlled in the range of 35 to 55 ° C .;
2. The composite is preliminarily produced and dispersed in the polyol component by stirring and mixing the polyol component containing at least a fatty acid amide, a clay mineral filler, and silicone at a temperature of 35 to 48 ° C.,
3. The average particle size of the composite is in the range of 20 to 150 μm;
Is preferred.

In the method for producing a metal cap of the present invention, a composite composed of a fatty acid amide, a clay mineral filler and silicone is efficiently generated and dispersed in a polyurethane elastomer composition constituting a liner material applied to the metal cap. As a result, the fatty acid amide and silicone, which are the lubricant components together with the clay mineral filler, can uniformly coat the entire surface of the liner material, and the amide re-dissolution phenomenon described above hardly occurs, and the fatty acid that is the sliding component. The amide can uniformly coat the entire surface of the liner material, and it is possible to provide a metal cap having excellent openability even when stored in a sealed state for a long time.
In the method for producing a metal cap of the present invention, a metal cap having excellent openability can be produced using a conventional lining apparatus, and the productivity and economy are also excellent.
The polyurethane elastomer composition used in the present invention is also excellent in lining properties, and can efficiently form a liner material on a metal cap.
Furthermore, the liner material formed on the metal cap of the present invention is excellent in sealing performance, safety and hygiene.

It is a figure which shows an example of the manufacturing line used for the manufacturing method of the metal cap of this invention.

The present invention relates to a method for producing a metal cap in which a polyurethane elastomer composition is applied to the inner surface of a metal cap shell, and this is heated and cured to form a liner material, the polyurethane elastomer composition comprising a fatty acid amide, A two-component polyurethane elastomer comprising a polyol component and a polyisocyanate component containing a clay mineral filler and silicone, and comprising a fatty acid amide, a clay mineral filler and silicone in the polyurethane elastomer composition applied to the metal cap It is an important feature that the complex is generated and dispersed.
As described above, conventionally, a metal cap having a liner material made of a polyurethane elastomer composition composed of the above-described components has a problem that it becomes inferior in opening performance with time.
As a result of investigating the cause of such a problem, the present inventors have found that the lubricant is not evenly present on the surface of the liner material and is only partially present in the liner material formed on the metal cap that causes such a problem. I found out that I did not. That is, when the lubricant is present in the polyurethane elastomer composition in a dissolved state, the lubricant is present not only on the liner material surface but also below the liner material in the thickness direction. As a result, the entire surface of the liner material is lubricated. Is not covered.

In order to allow the lubricant to uniformly exist on the surface of the liner material, the present inventors include a composite mainly composed of a lubricant composed of a fatty acid amide, a clay mineral filler, and silicone in a polyurethane elastomer composition applied to a cap. By forming and dispersing, when the polyurethane elastomer composition is applied to the cap, the composite rises to the vicinity of the surface, and by baking this, the fatty acid amide melts, and the surface of the liner material formed is It has been found that the whole can be uniformly coated with a lubricant together with a clay mineral filler, and it has become possible to effectively solve the deterioration of the openability with time.
Such operational effects of the present invention are also apparent from the results of Examples described later.
That is, a liner material made of a polyurethane elastomer composition in which a complex composed of a fatty acid amide, a clay mineral filler and a silicone is dispersed has a low opening torque even after storage over time, and has an excellent opening property. (Examples 1 to 4), whereas such a composite was not finally formed in the polyurethane elastomer composition, the polyurethane elastomer composition in which the fatty acid amide was present alone (state) It is clear that the liner material made of a product has an increased opening torque after storage over time and is inferior in the opening performance (Comparative Examples 1 to 6).

(Preparation of polyurethane elastomer composition and formation of liner material)
In the present invention, in order to prepare a polyurethane elastomer composition in which a composite composed of a fatty acid amide, a clay mineral filler, and silicone is dispersed, at least a polyol component containing a fatty acid amide, a clay mineral filler, and silicone is contained in 35 to It is important to stir and mix at a temperature of 48 ° C., particularly 40 to 48 ° C.
The stirring speed during the stirring and mixing is preferably carried out by stirring and mixing for 30 to 90 minutes at a maximum peripheral speed of 100 m / min or less, particularly 30 to 60 m / min.
That is, in order to form a complex composed of a fatty acid amide, a clay mineral filler, and a silicone, it is not desirable to add a fatty acid amide, a clay mineral filler, and a silicone to a highly reactive isocyanate component, and the isocyanate component and the polyol. If the fatty acid amide, clay mineral filler, and silicone are blended after mixing the ingredients, stirring and mixing that can form a composite cannot be performed sufficiently, so the fatty acid amide, clay mineral filler, and silicone are added to the polyol component. It is desirable to mix and produce these complexes in advance.
In the apparatus shown in FIG. 1 to be described later, the polyol component and the isocyanate component are kneaded in a short time in the kneading part, so that the polyol component supplied to the kneading part must already contain a composite. However, a composite can be formed in the kneading part by kneading the polyol component and the isocyanate component for 30 minutes or more.

In the present invention, it is also important to stir in the above temperature range. That is, by stirring in the above temperature range, the fatty acid amide in the polyol component is precipitated, and the precipitated fatty acid amide is bound to the clay mineral filler and silicone, thereby forming a composite.
In addition, since the silicone is inferior in compatibility with the polyol component, this composite has a dispersion structure in which the average particle size is 20 to 150 μm, particularly 70 to 130 μm, dispersed in the polyol component. In the polyurethane elastomer composition having a stable dispersion structure, the composite was maintained in a dispersed state in the polyurethane elastomer composition by controlling the temperature in the range of 35 to 55 ° C., particularly 40 to 48 ° C. The metal cap shell can be supplied as it is. When this temperature range is exceeded, the complex is not formed because the fatty acid amide exists alone in the molten state particularly on the high temperature side. Also, when the temperature is lower than this temperature range, a composite is formed, but the viscosity of the polyol component or polyurethane elastomer composition is increased, so that a stable amount of stable discharge work becomes difficult, resulting in poor liner shape. There is a possibility that a problem relating to the workability of molding, such as easy to do, may occur.

FIG. 1 is a schematic view of an example of a production line of a method for producing a gold cap according to the present invention.
In the method for producing a metal cap of the present invention, in a polyol component tank 1 having a stirring blade, a polyol component in which a fatty acid amide, a clay mineral filler, silicone, and other compounding agents described below are blended with a polyol is stirred. After mixing and forming a complex composed of a fatty acid amide, a clay mineral filler, and silicone in the polyol, it is transferred to the polyol component quantitative supply unit 2. At this time, as described above, it is important to stir, mix and transfer in the temperature range of 35 to 55 ° C., and it is preferable to stir and mix at the above stirring speed.
On the other hand, the isocyanate in the isocyanate tank 3 is transferred to the isocyanate component quantitative supply unit 4.

Next, the polyol component in the polyol component quantitative supply unit 2 and the isocyanate component in the isocyanate component quantitative supply unit 4 are each quantified and supplied to the kneading unit 5. In the kneading part 5, as described above, the temperature is controlled to a temperature of 35 to 55 ° C. Thus, in the polyurethane elastomer composition prepared by the reaction of the polyol and the isocyanate in the drying oven, the composite is contained. Maintained in a distributed state. In the kneading section 5, the polyol component and the isocyanate component are kneaded with the screw, and at the same time, the composite-dispersed polyurethane elastomer composition is transferred to the quantitative supply valve 6. A fixed amount supply valve 6 supplies a fixed amount of the composite dispersed polyurethane elastomer composition from the lining nozzle 7 to the metal cap shell 9 fixed on the rotary mounting portion 8. The supply timing of the polyol component quantitative supply unit 2 and the isocyanate component quantitative supply unit 4 is synchronized with the timing of the quantitative supply valve 6, and when the quantitative supply valve 6 discharges the polyurethane elastomer composition, the polyol component quantitative supply is performed. The part 2 and the isocyanate component quantitative supply part 4 supply the polyol component and the isocyanate component to the kneading part 5, respectively.
Next, although not shown, the metal cap coated with the polyurethane elastomer composition is transferred to a drying oven and cured by heating under a heating condition of 150 to 300 ° C. for 20 to 200 seconds. The material is formed and a metal cap is produced.

(Polyurethane elastomer composition)
The polyurethane elastomer constituting the liner material in the present invention is a two-component polyurethane elastomer obtained by heat-curing a prepolymer comprising an isocyanate component and a polyol component.
As the isocyanate component, aliphatic and / or alicyclic isocyanates can be suitably used. For example, hydrogenated aromatic isocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), lysine diisocyanate and the like can be used. Can be mentioned. Examples of the aromatic polyisocyanate include tolylene diisocyanate and diphenylethane diisocyanate. Among these, HDI and / or IPDI can be preferably used.
Further, the above-mentioned isocyanate component may be modified, and dimerization reaction, trimerization reaction, high polymerization reaction of aliphatic and / or alicyclic isocyanate, (each) isocyanate and polyfunctional active hydrogen group-containing It is preferable to obtain by urethanation reaction with a compound, urea reaction, amidation reaction, and further modification by allophanatization reaction and biuretization reaction.

  The isocyanate group content of the isocyanate component is preferably 5 to 38% by mass, particularly 8 to 25% by mass. When the isocyanate group content is less than 5% by mass, the viscosity is too large to be handled easily, and when it exceeds 38% by mass, it is substantially difficult to suppress the concentration of the free raw material isocyanate to 1% by mass or less. The isocyanate group content here is the content of the isocyanate group when reacting with the polyol component and does not show activity as an isocyanate group at room temperature, but regenerates the isocyanate group at a high temperature. For example, two isocyanate groups are present. It is a concept including an uretdione group polymerized in a cyclic manner and an isocyanate group from a uretonimine bond in which one isocyanate group is added to a carbodiimide group. The average number of functional groups of the aliphatic isocyanate is 2 to 3 from the viewpoint of the amount of eluate of polyurethane elastomer and compression set.

As the polyol, it is preferable to use a polymer polyol having a number average molecular weight of 200 to 2,000. Specific examples thereof include polypropylene glycol polyether polyol (PPG), polytetramethylene ether glycol (PTMG) and adipate polyester polyol, polycaprolactone polyester polyol, polycarbonate polyol and the like. From the viewpoint of eluate of polyurethane elastomer, PTMG and adipate polyester polyol are preferable. From the viewpoint of hydrolysis resistance, PTMG and PPG are more preferable.
In the present invention, the polyol most preferably used for sealing material has a hydroxyl value of 20 to 350 (mgKOH / g), preferably 100 to 350 (mgK0H / g). When the hydroxyl value is less than 20 (mgKOH / g), the resulting polyurethane elastomer is too soft and the compression set becomes too large. When it exceeds 350 (mgKOH / g), it is too hard and unsuitable as a sealing material. It is. The average number of functional groups of the polyol is preferably 2 to 3, corresponding to the average number of functional groups of the isocyanate component, since an appropriate amount of a crosslinked structure is preferably introduced into the polyurethane elastomer.

Further, when a polyurethane elastomer is synthesized by reacting an isocyanate component and a polyol component, the isocyanate component is used in an amount of 1 mol of active hydrogen atoms with respect to the total amount of active hydrogen atoms of the polyol component and other components. It is preferable to use it at a ratio that the number of moles of the isocyanate group per unit becomes 0.9 to 1.5 mol, and it is further preferable to use it at a ratio that becomes about 1.00 to 1.10 mol.
As a method for synthesizing the polyurethane elastomer in the present invention, any of known urethanation reaction techniques can be used, and either a prepolymer method or a one-shot method may be used.
The polyurethane elastomer used in the sealing material of the present invention has a potassium permanganate consumption of 15 ppm or less, particularly 10 ppm or less when the retort treatment is performed at 125 ° C. for 30 minutes with 10 ml of water per 1 g of the polyurethane elastomer. It is preferable that.

In the polyurethane elastomer composition constituting the liner material in the present invention, at least a fatty acid amide, a clay mineral filler, and silicone are blended in the two-component polyurethane elastomer composed of the above-described polyol component and polyisocyanate component.
In the present invention, the fatty acid amide, the clay mineral filler, and the silicone are desirably blended in advance in the polyol component as described above, and the fatty acid amide is 10 to 20 parts by weight, especially 10 parts by weight based on 100 parts by weight of the polyol. It is preferably contained in an amount of 17 to 17 parts by weight. When the fatty acid amide content is less than the above range, the unplugging property becomes inferior. On the other hand, even if the fatty acid amide content is larger than the above range, further improvement in the opening property is expected. Rather, the fatty acid amide is not preferred because it may elute into the contents.
The clay mineral filler is preferably contained in an amount of 15 to 50 parts by weight, particularly 18 to 42 parts by weight, based on 100 parts by weight of the polyol. When the content of the clay mineral filler is less than the above range, the fatty acid amide and the silicone cannot be sufficiently supported, and it may be difficult to form a complex sufficient to improve the opening performance. In addition, when the polyurethane elastomer composition is baked and cured under the heating conditions described above, the shape cannot be maintained and the moldability becomes poor. On the other hand, when there is more content of a clay mineral filler than the said range, workability | operativity and a moldability will become inferior.
Furthermore, the silicone is preferably contained in an amount of 2 to 7 parts by weight, particularly 3 to 5 parts by weight, based on 100 parts by weight of the polyol. When the silicone content is less than the above range, it may not be possible to form a dispersion structure in which the composite having the above-mentioned particle size is dispersed, and the openability may not be improved sufficiently. Even if the silicone content is larger than the above range, further improvement in the opening property cannot be expected, and the cost becomes inferior.

Examples of the fatty acid amide include stearic acid amide, oleic acid amide, erucic acid amide, and the like, and erucic acid amide can be particularly preferably used.
Examples of the clay mineral filler include talc, calcined clay, mica, bentonite, kaolin, montmorillonite, and talc can be particularly preferably used.
The polyurethane elastomer composition used in the present invention can be blended with conventionally known additives such as a reaction catalyst and an antioxidant according to a conventionally known formulation.

(Metal cap)
The metal cap used in the present invention can take various forms. However, in the present invention, since the opening torque is improved, the cap that is opened by turning, particularly the screw at the container mouth portion, is used. A cap that is fixed is preferred.
As the metal material constituting the metal cap shell, various aluminum materials and various steel plates that have been conventionally used for metal caps can be used. Examples of the aluminum material include pure aluminum and aluminum and other alloy metals, particularly aluminum alloys containing a small amount of magnesium, manganese, etc., and various steel sheets include chromate surface-treated steel sheets, particularly electrolytic chromic acid. A treated steel plate can be mentioned.
The metal material is preferably provided with a protective coating made of a polyester paint or a protective coating made of polyester resin.

(Examples 1-4 and Comparative Examples 1-6)
As a polyol component, a polytetramethylene ether glycol PTG-1000SN manufactured by Hodogaya Chemical Industry, a Kuraray adipate-based polyester glycol P-1010, and a Kuraray-made adipate-based polyester triol in a liquid state having a number average molecular weight of 890 are prepared. As the isocyanate component, a viscous liquid prepolymer having a number average molecular weight of 430 and an average functional group number of 2 obtained by reacting HDI (hexamethylene diisocyanate) and 1,3-BG (butylene glycol) was used.
Fatty acid amide (1: 1 blend of erucic acid amide ALFLOW-P10 and oleic acid amide ALFLOW-E10 manufactured by Nippon Oil & Fats), clay mineral filler (mica only in Example 2, Others use talc), silicone (1: 1 blend of Shin-Etsu Chemical KF-96-1000, KF-96-300), reaction catalyst dioctyl tin maleate polymer and antioxidant Ciba Specialty Chemicals IRGANOX 1010 was blended and stirred at the temperature shown in Table 1 for 60 minutes at a peripheral speed of stirring speed of 30 m / min. In this case, the state of the fatty acid amide was examined by the following method in order to make it easily visible. Next, this polyol component was mixed with the isocyanate component at the temperature shown in Table 1 to prepare a polyurethane elastomer composition, and the presence or absence of a composite in the polyurethane elastomer composition was examined by the following method. This polyurethane elastomer composition was applied to the inner surface of a 63φ aluminum twist-off cap and heated at a temperature of 215 ° C. for 50 seconds to form a liner material. The distribution of the composite on the outermost surface of the liner material was examined by the following method. Further, the opening torque of the obtained metal cap was measured. The results are shown in Table 1.

(Measuring method)
-State of fatty acid amide A fatty acid amide, a clay mineral filler and silicone are blended in advance in a polyol component, and the polyol component obtained by stirring and mixing is heated at the temperature shown in Table 1 and visually observed 30 minutes later. When the fatty acid amide is dissolved, the state is determined from the transparency.
-Confirmation of presence / absence of composite and particle diameter 0.001 g of polyurethane elastomer composition is placed on a slide glass, and a cover glass is placed thereon. A weight of 170 g is applied here for 5 seconds and stretched thinly, and using an optical microscope, the presence or absence of a composite in the composition is confirmed and the particle size is measured at a magnification of 100 times or less.
-Distribution of the composite on the surface of the liner The liner portion of the cap is cut off, the surface is washed with a solvent (tetrahydrofuran), and then the surface of the liner is observed at a magnification of 10 using an electron microscope. By observing the clay mineral filler in the composite, it was used as a substitute for confirming the distribution of the composite itself.
-Moldability and workability The shape of the liner after baking of the polyurethane elastomer composition, the liner moldability of the surface smoothness, and the workability during discharge were confirmed.
-Opening torque Each of the metal caps obtained as a result of the preparation was wound around a glass bottle. (Filling condition: filled with 360 g of hot water at 90 ° C., heat sterilization treatment condition: a hot water shower at 95 ° C. was applied to the cap for 10 minutes) Then, as an acceleration treatment of the phenomenon of increasing the opening torque, 9 hours in a 50 ° C. environment After repeating 15 hours in a + 23 ° C. environment twice, the opening torque of each sample was measured.

In the method for producing a metal cap of the present invention, in the liner material having the same composition as the conventional polyurethane elastomer composition, it is possible to uniformly coat the entire surface of the liner material with the fatty acid amide, and an excellent opening Therefore, the cap can be suitably used for a cap that is opened by turning, in particular, a cap that is screwed to the container mouth portion.
Moreover, since all the raw materials to be used are excellent in safety and hygiene, they can be used for the production of caps containing beverages, foods and the like.
Furthermore, in the method for producing a metal cap according to the present invention, a metal cap having excellent openability after storage over time can be produced using a conventional lining device. Is also excellent.

  DESCRIPTION OF SYMBOLS 1 Polyol component tank, 2 Polyol component fixed supply part, 3 Isocyanate component tank, 4 Isocyanate component fixed supply part, 5 Mixing part, 6 Fixed supply pump, 7 Lining nozzle, 8 Rotation mounting base, 9 Metal Cap shell.

Claims (4)

In the method for producing a metal cap, a polyurethane elastomer composition is applied to the inner surface of the metal cap shell, and this is heated and cured to form a liner material.
The polyurethane elastomer composition is a two-component polyurethane elastomer comprising a polyol component and a polyisocyanate component containing a fatty acid amide, a clay mineral filler, and silicone, and the polyurethane elastomer composition applied to the metal cap, A method for producing a metal cap, wherein a composite comprising a fatty acid amide, a clay mineral filler and silicone is dispersed.   The method according to claim 1, wherein the temperature of the polyurethane elastomer composition containing the composite is controlled in the range of 35 to 55 ° C.   The composite is produced and dispersed in advance in a polyol component by stirring and mixing a polyol component containing at least a fatty acid amide, a clay mineral filler, and silicone at a temperature of 35 to 48 ° C. The manufacturing method as described.   The manufacturing method according to any one of claims 1 to 3, wherein an average particle size of the composite is in a range of 20 to 150 µm.

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