PACKING MEMBER HAVING SURFACE EXCELLENT IN LIQUID REPELLENCY

Abstract

A packing member which effectively prevents the liquid repellent material from peeling off the surface and which is provided with the surface excellent in liquid repellency without the need of executing any particular means such as surface-roughening work, treatment with a plasma or vapor deposition. The packing member is characterized by having a surface layer of a blend of a base material polymer mixed with a fluorine-containing polymer, the surface layer forming a gradient of fluorine atom concentration in which fluorine atoms are more distributed in the surface than in the interior.

Claims

1. A packing member having a liquid repellent surface characterized by having a surface layer of a blend of a base material polymer mixed with a fluorine-containing polymer, said surface layer forming a gradient: of fluorine atom concentration in which fluorine atoms are more distributed in the surface than in the interior.

2. The packing member according to claim 1, wherein said surface shows a water repellency of not less than 105 degrees in terms of the water contact angle.

3. The packing member according to claim 1, wherein said surface is a smooth surface having an arithmetic mean surface roughness (Ra) of not more than 10 m.

4. The packing member according to claim 1, wherein said fluorine-containing polymer is a fluorine-containing acrylic resin or a fluorine-containing silicone resin.

5. The packing member according to claim 1, wherein. said. base material polymer is a polyolefin or a polyester.

6. The packing member according to claim 1, wherein said blend contains the fluorine-containing polymer in an amount of 0.01 to 50 parts by mass per 100 parts by mass of the base material polymer.

7. The packing member according to claim 1, wherein the surface layer of said blend has a layer-laminated structure formed on at least one surface of the underlying base material.

8. The packing member according to claim 7, wherein said packing member is a nozzle for ejecting an eye lotion.

9. The packing member according to claim 7, wherein said packing member is a cap.

10. The packing member according to claim 7, wherein said packing member is a pouch.

11. A. method of producing a packing member having a liquid repellent surface, characterized by using a blend of a base material polymer mixed with a fluorine-containing polymer to obtain a packing member whose surface is made of said blend and, thereafter, subjecting the surface of said packing member to a migration treatment in which the surface of said packing member is held at a temperature of not lower than 30 C. but lower than 160 C. for not shorter than one second.

Description

BRIEF DESCRIPTION OF THE DRAWING:

[0036] FIG. 1 It is a model diagram illustrating the surface state of a packing member of the present invention.

MODES FOR CARRYING OUT THE INVENTION

[0037] Referring to FIG. 1, the packing member of the present invention has a layer-laminated structure in which a surface layer 1 is formed on the surface of an underlying base material 3.

[0038] In the invention, the surface layer 1 is a blend of a base material polymer and a fluorine-containing polymer. In a surface 1a thereof, there are distributed fluorine-containing groups Rf of the fluorine-containing polymer as they are migrated to exhibit a large degree of liquid repellency against a variety of liquids.

[0039] As the fluorine-containing polymer, there can be exemplified polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE) polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxyfluorine resin (PFA), ethylene tetrafluoride propylene hexafluoride copolymer (FEP), ethylene ethylene tetrafluoride copolymer (ETFE), and ethylene chlorotrifluoroethylene copolymer (ECTFE). The invention particularly preferably uses the fluorine-containing acrylic resin and the fluorine-containing silicone resin from the standpoint of migration property and affinity to the base material polymer.

[0040] The above fluorine-containing acrylic resin is a fluorine-containing acrylic resin represented, for example, by the following formula:

RfCH.sub.2CH.sub.2OOC(CX)=CH.sub.2 [0041] wherein Rf is a fluorine-containing alkyl group such as perfluoroalkyl group, and X is a hydrogen atom or an alkyl group such as methyl group.

[0042] The invention preferably uses a polymer obtained by polymerizing the above fluorine-containing acrylic resin.

[0043] Further, the fluorine-containing silicone resin is a polyorganosiloxane represented, for example, by the following formula:

(RO).sub.2RfSiO(RORfSiO)n-SiRf(OR).sub.2 [0044] wherein R is a hydrogen atom or an alkyl group such as methyl group, Rf is a fluorine-containing group such as fluoroalkyl group, and n is a number representing the degree of polymerization.

[0045] In the invention, the above-mentioned fluorine-containing polymer is said to be, preferably, the one in which the fluorine-containing group has a molecular weight which is, usually, less than C8 telomer from the standpoint of safety.

[0046] The base material polymer blended with the above fluorine-containing polymer is a resin that contains no fluorine. Use of this base material polymer makes it possible to secure a close adhesion to the base material 3 that lies under the surface layer 1. Besides, the fluorine-containing distributed in the surface 1a as it has migrated can be firmly held in the surface layer 1.

[0047] As the base material polymer, there can be used either a thermoplastic resin or a thermosetting resin. However, the thermoplastic resin is preferred from the standpoint of, specifically, formability and migration property of the fluorine-containing polymer.

[0048] As the thermoplastic resin, there can be exemplified:

[0049] olefin resins such as low-density polyethylene, high-density polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene or random or block copolymers of -olefins, such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, or cyclic olefin copolymers;

[0050] ethylene vinyl copolymers such as ethylene vinyl acetate copolymer, ethylene vinyl alcohol copolymer and ethylene vinyl chloride copolymer;

[0051] styrene resins such as polystyrene, acrylonitrile styrene copolymer, ABS, and -methylstyrene styrene copolymer;

[0052] vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl cloride vinylidene chloride copolymer, methyl polyacrylate, and methyl polymethacrylate;

[0053] polyamide resins such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12;

[0054] polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate and copolymerized polyesters thereof;

[0055] polycarbonate resin;

[0056] polyphenylene oxide resin; and

[0057] biodegradable resin such as polylactic acid.

[0058] It is, of course, allowable to use a blend of these thermoplastic resins, and a suitable thermoplastic resin may be used depending on the packing member that is used.

[0059] In the field of packing, for example, olefin resins and polyester resins can be preferably used.

[0060] In the invention, further, the blend of the base material polymer and the fluorine-containing resin that forms the surface layer 1, is, desirably, the one which contains the fluorine-containing polymer in an amount of 0.01 to 50 parts by mass, preferably, 0.05 to 10 parts by mass, more preferably, 0.05 to less than 3 parts by mass and, particularly preferably, 0.1 to 1 part by mass per 100 parts by mass of the base material polymer. Even when the fluorine-containing polymer is contained in unnecessarily large amounts, the liquid repellency is not improved any more. In this case, rather, the result becomes unsatisfactory from the standpoint of cost and, besides, the surface layer 1 tends to be easily peeled off the underlying base material 3. When the fluorine-containing polymer is contained in small amounts, on the other hand, the liquid repellency cannot be secured to a sufficient degree despite the migration treatment (heating treatment) is conducted as described later.

[0061] The surface layer 1 of the above blend forms a gradient of fluorine atom concentration through the migration treatment that will be described later and, therefore, the fluorine atoms are present at a higher concentration in the surface 1a than in the interior of the surface layer 1. Namely, as shown in FIG. 1, the fluorine-containing functional groups Rf possessed by the fluorine-containing polymer are so distributed as to be exposed on the side of the surface 1a. Accordingly, more excellent liquid repellency is exhibited than when the fluorine-containing polymer is homogeneously dispersed in the surface layer 1.

[0062] According to the invention, excellent liquid repellency can be confirmed by measuring the water contact angle. For example, as demonstrated in Examples appearing later, the surface 1a of the packing member of the invention exhibits a water contact angle of not less than 105 degrees (as measured at 23 C.) and is forming a water-repellent surface.

[0063] In the invention, further, the underlying base material 3 may be made of a suitable material depending on the use of the packing member and may, for example, be made of plastic, paper or metal. From the standpoint of adhesiveness to the surface layer 1, however, the underlying base material 3 should, preferably, be made of plastic or paper. To secure adhesiveness to the surface layer 1, furthermore, the underlying base material 3 may be made of an adhesive resin that is known per se.

[0064] Further, the underlying base material 3 can be formed in a multilayered structure using, as an intermediate layer, a gas-barrier resin as represented by an ethylene-vinyl alcohol copolymer.

[0065] In the invention, from the standpoint of formability and close adhesion, it is most desired that the surface of the underlying base material 3 which is in contact with the surface layer 1 is made of an olefin resin or an ester resin and, specifically, the olefin resin.

[0066] According to the invention, the packing member, in principle, can be formed in a single-layer structure comprising the above-mentioned blend only without having the underlying base material 3 provided the surface layer 1 is formed by using the blend that contains the above-mentioned fluorine-containing polymer forming therein the gradient of fluorine atom concentration. In this case, however, the expensive fluorine-containing polymer must be used in an increased amount, which is a disadvantage in cost and posing large limitation in the use. It is, therefore, desired that the packing member has a layer-laminated structure forming the surface layer 1 on the underlying base material 3.

[0067] In the invention, the underlying base material 3 may. assume a suitable form depending on the use, such as bottle, film, bag, cup, paper cup, container lid or spout. It may, further, assume such a form as nozzle, dispenser, pipette or pipette tip. Namely, the underlying base material 3 can be used as various members that come in contact with the liquid when it is in use, as a container or as a member to be fitted to the container, as a member for collecting a liquid upon sucking and for discharging the liquid, and as a member that is used being fitted thereto.

[0068] The above-mentioned surface layer 1 can be formed by preparing a coating solution by dissolving or dispersing, in a suitable volatile organic solvent, the above-mentioned blend of the base material polymer and the fluorine-containing polymer, applying the coating solution onto the surface of the underlying base material 3 that has been formed in a predetermined shape in advance, and drying the toting solution. Depending on the shape of the underlying base material 3 that is formed, the coating solution can be applied by spraying, brushing, dipping, screen-coating, or roll-coating.

[0069] Further, when the underlying base material 3 is a plastic, a resin composition is prepared by melting and kneading the base material polymer and the fluorine-containing polymer together, and subjecting the resin composition to an integral forming such as co-injection or co-extrusion.

[0070] The packing member having the surface layer 1 is obtained as described above and is then put to the migration treatment. There is thus obtained the packing member of the present invention having a predetermined fluorine concentration profile and a surface that is more excellent in liquid repellency.

[0071] In the invention, the migration treatment is carried out by holding at least the surface layer 1 at a temperature of not lower than 30 C. but lower than 160 C. for not shorter than one second.

[0072] If the migration treatment is carried out at a temperature of not lower than 160 C. which temperature being higher than a temperature at which the olefin resin and the polyester resin undergo a thermal deformation, then the underlying base material also often undergoes a thermal deformation such as shrinking and wrinkling.

[0073] Further, if the migration treatment is carried out at a temperature lower than the above-mentioned temperature, the fluorine-containing polymer migrates insufficiently. In this case, even if the liquid repellency could be improved by the migration, a very extended period of time is required for the migration treatment, which, therefore, cannot be employed for industrial use.

[0074] Moreover, if the migration treatment is carried out for only a short period of time, the fluorine-containing polymer is migrated only insufficiently and improved liquid repellency cannot be expected. Upon conducting the heat treatment at a predetermined temperature for not shorter than one second as described above, it is allowed to obtain a water repellent surface having a water contact angle of not less than 105 degrees. For example, when the heat treatment is conducted by using a laser of a carbonic acid gas for which the plastic shows a high coefficient of absorption, the surface layer 1 is locally heated and the migration is accomplished despite the heat treatment is conducted for only one second.

[0075] Carrying out the migration treatment for unnecessarily long periods of time results in a decrease in the productivity. Concerning the treatment time, therefore, it is recommended to, first, conduct the testing on a laboratory scale to make sure the period of time in which the desired water contact angle of not less than 105 degrees and, specifically, about 110 degrees can be obtained to thereby avoid excess of treating time.

[0076] As described above, upon conducting the migration treatment as contemplated by the present invention, it is made possible to realize the water repel lent surface having a water contact angle of not less than 105 degrees and, specifically, not less than 110 degrees. For example, it has been known that upon carrying out the treatment with a fluorine plasma, there can be obtained a water repellent surface due to the roughening of the surface and due to the introduction of the fluorine atoms. Without dare to carry out the treatment by using such an expensive apparatus, however, the present invention made it possible to realize the water repellent surface that is equivalent to that of when the treatment with the fluorine plasma is carried out.

[0077] Moreover, the packing member of the present invention does not have to be roughened for its surface by, for example, etching. Accordingly, the packing member features a smooth surface, e.g., an arithmetic mean roughness Ra of not more than 10 m on the surface layer 1a.

[0078] The packing member of the present invention exhibits very excellent repellency against a variety of liquids, and is effective in such uses where the formed surface 1a comes in contact with various liquids, e.g., in a field of packing like bottles, cups, pouches, glasses, container lids and spouts, effectively preventing dripping of liquid and adhesion of liquid.

[0079] Besides, the surface 1a of the packing member has a favorable liquid-dispelling property, and can be favorably adapted to such uses as nozzles, dispensers, pipettes, pipette tips, etc.

EXAMPLES

Example 1

(Preparation of Samples)

[0080] A low-density polyethylene resin (LJ8041 produced by Japan Polyethylene Co.) or a polypropylene (J246M produced by Prime Polymer Co.) blended with a fluorine-containing polymer (Asahi Guard AG-E060 produced by AGC Co. or DAIFREE FB962 produced by Daikin Industries, ltd.) in a predetermined amount, was melt-kneaded by using a kneader at a temperature higher than a melting point of the low-density polyethylene resin or the polypropylene.

[0081] The kneaded product was milled by using an electric mill and was pelletized.

[0082] The pellets were heated and pressed by using an electric hot press, and was formed into a film 100 m in thickness.

[0083] The thus formed film was dry-laminated on a biaxially stretched PET film 12 m in thickness via an adhesive to obtain samples which were then stored in an electric oven set at a predetermined temperature for a predetermined period of time to have the fluorine-containing polymer migrated.

(Evaluation)

[0084] The samples before and after stored in the electric oven, i.e., the samples before and after the fluorine-containing polymer has migrated, were measured for their water contact angles under the following conditions. [0085] Liquid: pure water, 5 L [0086] Measuring apparatus: DropMaster 700 manufactured by Kyowa Interface Science Co., Ltd.

[0087] The samples before stored in the electric oven were measured for their surface roughness (arithmetic mean roughness Ra) by using a white color interferometer under the following conditions. [0088] Measuring apparatus: New View 7300 manufactured by ZYGO Co. [0089] Objective lens, magnifying power of 50 [0090] Eyepiece, magnifying power of 2.0 [0091] Long wavelength cut-off value c=13.846155 m [0092] Short wavelength cut-off value s=346.155 nm

(Evaluated Results)

[0093] The evaluated results were as shown in Table 1 below.

[0094] The low-density polyethylene resin bulk material exhibited water contact angle of 90 and, therefore, the water contact angles were evaluated in a manner as described below. [0095] : 110 [0096] : 105 to 109 [0097] X: 104 or could not be measured due to thermal deformation.

[0098] This Example proved that excellent liquid repellency could be expressed. without the need of executing any particular means such as surface-roughening treatment or treatment with a plasma.

Comparative Example

[0099] Samples were prepared under the same conditions as in Example above but storing them in the electric oven under a condition of 180 C. for one minute to have the fluorine-containing polymer migrated.

[0100] The evaluated results were as shown in Table 1 below.

[0101] The samples shrunk greatly and wrinkled. Therefore, the water contact angle could not be measured.

TABLE-US-00001 TABLE 1 Conditions for preparing samples Evaluated results Base F-containing polymer Storage condition Water contact angle material Trade Parts Temp. Ra Before After polymer name by mass ( C.) Time (m) stored stored Ex. polyethylene Asahi 0.1 30 10 days 8.1 Guard 60 96 hrs 8.1 90 1 hr 8.1 polypropylene 125 30 min 8.1 155 5 min 8.1 Comp. Ex. 180 1 min 8.1 X Ex. polyethylene 1.0 30 10 days 8.1 60 96 hrs 8.1 90 1 hr 8.1 polypropylene 125 30 mins 8.1 155 5 min 8.1 Comp. Ex. 180 1 min 8.1 X Ex. polyethlene DAIFREE 0.1 30 10 days 8.1 60 96 hrs 8.1 90 1 hr 8.1 polypropylene 125 30 min 8.1 155 5 min 8.1 Comp. Ex. 180 1 min 8.1 X Ex. polyethylene 1.0 30 10 days 8.1 60 96 hrs 8.1 90 1 hr 8.1 polypropylene 125 30 min 8.1 155 5 min 8.1 Comp. Ex. 180 1 min 8.1 X

Example 2

(Preparation of a Sample)

[0102] The low-density polyethylene resin (LJ8041) blended with 0.1 part by mass of the fluorine-containing polymer (AG-E060) was melt-kneaded by using the kneader at a temperature higher than the melting point of the polyethylene resin.

[0103] The kneaded product was milled by using the electric mill and was pelletized.

[0104] A cap mold was mounted on an injection-forming machine. The pellets were thrown into a hopper of the injection-forming machine and were injection-formed at a cylinder temperature set at 180 C. into a sample cap.

[0105] Next, the sample cap was stored in the electric oven set at 90 C. for one minute to have the fluorine-containing polymer migrated.

[0106] The sample cap was fitted to a PET bottle that has been filled in advance with 300 mL of a sauce (Delicious Sauce Tonkatsu produced by Kikkoman Co.) to obtain a sample bottle.

(Evaluation Results)

[0107] The sample bottle was tilted to pour out the sauce. The amount poured out was about 3 mL each time. The pouring out was repeated about 100 times until there was left no sauce.

[0108] The cap after the pouring out was observed to find no occurrence of liquid dripping and no liquid left on the pour-out portion.

[0109] This Example proved that excellent liquid repellency could be expressed without the need of executing any particular means such as surface-roughening treatment or treatment with a plasma.

Example 3

(Preparation of a Sample)

[0110] The low-density polyethylene resin (LJ8041) blended with 1.0 part by mass of the fluorine-containing polymer (AG-E060) was melt-kneaded by using the kneader at a temperature higher than the melting point of the polyethylene resin.

[0111] The kneaded product was milled by using the electric mill and was pelletized.

[0112] A nozzle mold for eyedropper was mounted on the injection-forming machine. The pellets were thrown into the hopper of the injection-forming machine and were injection-formed at a cylinder temperature set at 180 C. into a sample nozzle.

[0113] Next, the sample nozzle was stored in the electric oven set at 90 C. for one minute to have the fluorine-containing polymer migrated.

[0114] The sample nozzle was fitted to a PET eyedropper that has been filled in advance with an eye lotion to obtain a sample eyedropper.

(Evaluation Results)

[0115] The sample eyedropper was held by hand in a manner that the nozzle was directed downward and perpendicularly. The sample eyedropper was then pushed to let the eye lotion dropped 100 times.

[0116] The amount that was dropped was measured by using the electronic Mettler. It was found that the amount dropped was 7 L on the average.

[0117] Further, a commercially available eye dropper on was also measured for its average amount of drop to be 30 to 50 L.

[0118] After the eye lotion is ejected from the ejection port, the surrounding of the ejection port becomes wet with the lotion over an expanded area to form a large liquid droplet. The liquid droplet starts dropping just as its own weight exceeds its force of adhesion to the surrounding of the ejection port. Therefore, a nozzle that wets well helps increase the amount of drop.

[0119] The nozzle according to this Example is imparted with excellent liquid repellency. It is, therefore, considered that the wettability decreases and the amount of drop decreases, too.

Example 4

(Preparation of a Sample)

[0120] The polypropylene (J246M) blended with 0.5 parts by mass of the fluorine-containing polymer (FB962) was melt-kneaded by using the kneader at a temperature higher than the melting point of the polypropylene resin.

[0121] The kneaded product was milled by using the electric mill and was pelletized.

[0122] The pellets were heated and pressed by using the electric hot press, and was formed into a film 60 m in thickness.

[0123] The thus formed film was dry-laminated on a 7 m-thick aluminum foil and a 12 m-thick biaxially stretched PET film via an adhesive. Thereafter, the two pieces of film were so overlapped that their polypropylene resin surfaces faced to each other, and the three sides were heat-sealed to obtain a sample pouch.

[0124] The pouch was filled with a curry (Curry House's curry <medium spicy> produced by House Foods Co.) and, thereafter, the remaining one side was heat-sealed to obtain a sample.

[0125] The sample was heated in an autoclave set at 125 C. for 30 minutes, and was then left to naturally cool down to normal temperature.

(Evaluation Results)

[0126] After the temperature of the sample has returned to normal temperature, one side that has been heat-sealed was cut open to pour the curry out.

[0127] After the curry was poured out, the inner surfaces of the sample were observed with the eye. There was left no curry and even the coloring matter of the curry could not be seen.

[0128] This Example proved that excellent liquid repellency could be expressed without the need of executing any particular means such as surface-roughening treatment or treatment with a plasma.

DESCRIPTION OF REFERENCE NUMERALS

[0129] 1: surface layer [0130] 1a: surface of the packing member [0131] 3: underlying base material