JPH0224855B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a highly adhesive polyolefin molded product, and more particularly to a polyolefin molded product that has sufficiently enhanced corona discharge treatment effects at a commercial production level and has improved adhesion to various materials. Corona discharge treatment of plastic films and molded materials has been carried out for a long time, and is an indispensable technique for surface modification of polyolefin films such as polyethylene and polypropylene, and its scope of application is increasingly expanding. It is expected that In order to deal with this situation, it is necessary to improve the processing efficiency of corona discharge itself and explore its possibilities, and although extensive improvement research has been carried out so far, it is still not sufficient. There is no situation. For example, as a corona discharge treatment method for plastic molded products, there is a technique that accelerates chemical changes on the discharge surface by supplying an organic solvent to the discharge area, as seen in Tokusho No. 48-17747. It is difficult to apply it to the molded products in question. or
Journal of Applied Polymer Science, Vol.
15, P., 1365-1375 (1971) describes a technique for performing corona discharge treatment in an inert gas atmosphere, and as the influence of the treatment atmosphere on activation or deterioration has been demonstrated, For example, techniques have been proposed that replace the process with a low-oxygen atmosphere. However, conventional methods of this type, such as the method disclosed in Japanese Patent Publication No. 56-18381, require a large amount of inert gas, resulting in high costs; (corona discharge technology under an inert atmosphere) requires a special shield structure to block the atmosphere that is entrained by the film, making the equipment complex, but even so, it is still difficult to maintain a completely or almost completely inert atmosphere. This was not guaranteed and we had to settle for a low processing level. The reason why conventional improvement processing methods cannot achieve sufficient results can be considered as follows. In other words, the key to increasing processing efficiency is thought to be the gas atmosphere in the discharge processing section, but conventional improvement methods only address the gas atmosphere within the processing system or chamber; This seems to be because the obstruction caused by accompanying flow (outside air) is not taken into consideration. Therefore, if the processing is carried out in a stationary state using the batch method, the above-mentioned problems will be alleviated, but this will significantly reduce industrial productivity and raise market prices, so it is only practical for limited applications. cannot be converted into Moreover, in order to obtain a high processing effect through continuous processing as described above, the processing speed has to be reduced, but this damages the surface of the object to be processed and causes problems such as poor appearance, poor adhesion, and increased blocking. It's derived. In the conventional corona discharge treatment under atmospheric conditions, the surface of the object to be treated is oxidized and oxidized deterioration products are generated on the surface, so even if the degree of treatment is advanced, the adhesion cannot be improved beyond a certain level. I can't. The present inventors have focused on these circumstances and have conducted research with the aim of developing a corona discharge treatment method that can provide polyolefin molded products with a high degree of adhesiveness at an industrial production level. The present invention was made as a result of such research, and consists of a polyolefin molded product subjected to corona discharge treatment while running through a corona discharge treatment device comprising at least one pair of electrodes facing each other, A gas having a higher nitrogen concentration than the air composition is applied to the corona discharge treated surface along the side wall surface of the discharge side electrode or from the bottom surface to the corona discharge treated surface of the polyolefin molded product at a rate of 1 of the speed at which the polyolefin molded product is introduced. % or more to destroy and disperse the entrained air layer, and to reduce the corona of the (O/C) ratio and (N/C) ratio in the thin layer portion within 100 Å from the surface of the polyolefin molded product. Ratio of change amount before and after discharge treatment [Δ(O/C)/Δ
(N/C)] is 1.8 or less, and the surface of the molded product is 100 Å.
After corona discharge treatment in subsequent thin layers (N/
C) A highly adhesive polyolefin molded product characterized by having a ratio of 3 or more. However, the gist lies in (O/C) ratio: number of oxygen per 100 carbons (N/C) ratio: number of nitrogen per 100 carbons. Polyolefin molded products to which the method of the present invention is applied include films, sheets, fibers, pipes,
Includes long items such as tape, woven fabrics, non-woven fabrics, etc.
Various known polyolefins can be used as the polyolefins constituting these molded products. Typical polyolefins for films or sheets include polyethylene, polypropylene, polybutene-1, and poly-4-methylpentene-1. Examples include homopolymers such as polyhexene, various copolymers containing about 70% by weight or more of propylene constituent units, and polyolefin blends containing about 40% by weight or more of propylene constituent units. In addition, stabilizers, lubricants, anti-blotting agents,
Additives such as antifogging agents, ultraviolet absorbers, flame retardants, clarifying agents, antioxidants, light stabilizers, antistatic agents, dyes, pigments, etc. may be included and do not adversely affect the implementation of corona discharge. Regardless of whether they are used singly or in combination, they are all included as objects of the present invention. In the present invention, the above-mentioned polyolefin molded product is treated, and the molded product is continuously passed through a corona discharge treatment device comprising at least one pair of electrodes for surface treatment. Along the wall surface or the bottom surface of the treated surface gas, along the wall surface of the discharge side electrode or from the bottom surface toward the molded article, the nitrogen concentration is higher than the air composition [specifically, an appropriate amount of O ₂ is removed from the air. N ₂ gas added to air, N ₂ gas alone, N ₂ and H ₂ , Ar, Co ₂ ,
A mixture of inert gases such as Xe and Kr and ionic gases (hereinafter referred to as high nitrogen concentration gas for convenience) is sprayed. The spraying speed is 1% or more of the feeding speed of the polyolefin molded product. As detailed later, (O/C) before and after corona discharge treatment in a thin layer within 100 Å of the surface to be treated.
By strictly regulating the ratio and (N/C) ratio, various materials (e.g. metals; various inks, especially cellulose-based inks, water-based inks, etc.; resins, such as vinylidene chloride alone or copolymers, functional It is possible to obtain a polyolefin molded product with extremely excellent adhesion to resins (base-containing resins, etc.). The structure and effects of the present invention will be clarified below based on the drawings of the embodiments, but the structure and arrangement of the discharge side electrodes, the shape of the cover, etc. shown in the drawings are only representative examples. Since the above is merely an example of application to plastic film, it is within the technical scope of the present invention to change the design on the condition that it does not go against the spirit of these descriptions. FIG. 1 is a sectional view of the main parts showing the implementation concept of the present invention,
FIG. 2 is a perspective view showing a part of the discharge side electrode, in which 1 is a metal drum, 2 is an electrode cover, and 3 is a perspective view showing a part of the discharge side electrode.
is the discharge side electrode, 4 is the gas supply pipe, 5 is the gas jet,
6 indicates a running film. That is, the film 6 is introduced from the direction of arrow B into the metal drum 1 rotating in the direction of arrow A, and is further pulled out in the direction of arrow C. , polyester, epoxy resin, sewage, chlorosulfonated polyethylene, EP
Under the influence of high-pressure corona generated by applying a high voltage of several thousand to tens of thousands of V at a high frequency of several hundred KC/S between the metal drum 1 covered with rubber etc. If so, ozone and nitrogen oxide are generated to generate carbonyl groups and carboxyl groups on the surface of the film 6, thereby polarizing the surface. On the other hand, in the conventional example, oxygen in the atmosphere generates oxidized deterioration products on the film surface that inhibit adhesion, thereby blocking the surface. However, in this example, the entire corona discharge atmosphere is isolated from the atmosphere by the electrode cover 2, and a gas outlet 5 is provided in the discharge electrode 3 to blow high nitrogen concentration gas toward the surface of the film 6. With this structure, the above-mentioned problems are eliminated and the corona discharge effect on the surface layer of the film 6 can be maximized. To explain this situation in more detail, a small amount of accompanying air layer is formed on the surface of the film 6 that enters at a fairly high speed in the direction of arrow B.
Even if the atmosphere in the corona discharge section is replaced with a high nitrogen concentration gas, the surface of the film 6 itself remains in an atmospheric atmosphere. Therefore, in carrying out the present invention, as shown in FIG. 3, high nitrogen concentration gas is strongly blown onto the film surface to destroy and disperse the accompanying air layer, and the accompanying air layer 7 is destroyed and dispersed by the jet stream 8. The film surface is almost completely replaced by the high nitrogen concentration gas. The flow velocity of the jet stream 8 necessary to destroy and disperse the entrained air layer 7 cannot be determined uniformly because it varies depending on the shape and method of the object to be treated, the speed of conveyance to the processing equipment, etc., but as a result of experiments, It has been found that it is most preferable to determine it based on the speed of entry of the air layer 7 (in other words, the speed of transport of the material to be treated). In other words, if the flow rate of the high nitrogen concentration gas is set to 1% or more, preferably 10% or more, and even more preferably 40% or more of the conveyance speed of the material to be treated, the accompanying air layer 7 can be formed to the extent that there is no practical problem. Can be removed. The speed at which the material to be processed is brought in is generally about 1 to 500 m/min. By adopting such conditions, it becomes possible to destroy and disperse the accompanying air layer, and at the same time, it becomes possible to protect the vicinity of the corona discharge part with a high nitrogen concentration gas atmosphere. The electrode cover 2 shown in the figure is expected to have a function of protecting the electrode 3 from mechanical shock and suppressing the accompanying flow even slightly, rather than a function of maintaining the atmosphere. . Therefore, when carrying out the present invention, the electrode cover 2 may be removed from time to time, but in order to suppress the consumption of high nitrogen concentration gas, it is desirable to reconsider its function for maintaining the atmosphere. For example, as shown in FIG. 4, if the lower end (film side) of the cover 2 is squeezed and at the same time high nitrogen concentration gas is introduced into the cover 2 from the conduit 10, the gas will be collected along the inner surface of the slope 9. The gas flows in the direction of the arrow, and a gas curtain effect is exerted at the inlet of the cover 2. That is, the intrusion of the entrained air layer is blocked on the inlet side, and the value of the electrode cover 2 is further improved. However, on the exit side of the film 6 (the right side in Fig. 4), the gas inside the cover 2 is discharged along with the traveling film 6, so the sealing performance or air infiltration barrier properties should be given the same consideration as on the entrance side. Although it is not necessary, it is meaningful to take the same consideration as on the inlet side in terms of reducing the consumption of high nitrogen concentration gas as described above. In order to achieve the above-mentioned sealing function on the inlet and outlet sides of the cover 2 to the minimum extent possible, it is discharged onto the film surface at a speed of at least 0.2% or more, preferably 10% or more relative to the film's walking speed. It is hoped that Regarding the ejection speed of the high nitrogen concentration gas, only the lower limit side has been described for both the gas ejection port 5 and the inlet/outlet of the cover 2, but there is no practical need to set an upper limit on the ejection speed, and it is determined based on economic efficiency and the requirements of the final product. It should be decided appropriately based on the balance with quality. By setting the processing conditions as described above, the processing effect of corona discharge is enhanced and the adhesion is greatly improved. We proceeded with further research, believing that it was necessary to quantitatively understand the surface characteristics before and after. As a result, the ratio of changes in (O/C) ratio and (N/C) ratio before and after corona discharge treatment in a thin layer within 100 Å on the surface of the treated object [Δ(O/C)/Δ(N /C)] and the (N/C) ratio after corona discharge treatment in a thin layer within 100 Å of the film surface, it has been found that a high degree of adhesion can be ensured. That is, for the above, [Δ(O/
C)/Δ(N/C)] is 1.8 or less, and for the above, the treatment conditions and atmosphere for corona discharge are strictly controlled so that (N/C) after treatment is 3 or more. For example, metals,
Adhesion to various printing inks (particularly cellulose inks, water-based inks, etc.), various synthetic resins such as vinylidene chloride alone or copolymer resins, and functional group-containing resins can be dramatically improved. There are various methods for measuring surface dynamics as described above, but the most suitable is the ESCA method. By the way, the present invention specifies [(N/C) ratio≧3]
Polyolefin molded products that meet the requirements of =
It can sometimes be obtained under conventional treatment conditions, and can also be achieved by known corona discharge treatment under a nitrogen gas atmosphere. However, as explained earlier, in order to secure the above-mentioned high level (N/C) ratio with the conventional method, which targets at least continuous processing, large-scale equipment is required, so it is difficult to put it into practical use on an industrial scale. was difficult. On the other hand, if the above method is adopted, the (N/C) ratio can be easily increased to 3 or more with relatively simple equipment. On the other hand, there is also a report that the adhesion of plastic materials to various materials is simply determined by the production ratio of N (relative to C) determined by the ESCA method. However, such reports capture only one aspect that affects adhesion. By the way, if you blend the N component into the material, the ratio (N/C) will increase, but the N
Considering the fact that simply mixing the antistatic agent and lubricant contained in the product does not improve adhesion, but rather reduces it, it is clear that an increase in the (N/C) ratio does not immediately correlate with adhesion. be. Therefore, we investigated other factors that affect adhesion and found the above [Δ(O/C)/Δ(N/
C)] is the corona discharge treatment effect,
In other words, it almost accurately represents the adhesion improvement effect, and this
It was confirmed that those treated to have a value of 1.8 or less exhibited a high level of adhesion suitable for the purpose. By the way, the surface layer after treatment is 100Å.
Even if (N/C) within the range is 3 or more, if [Δ(O/C)/Δ(N/C)] exceeds 1.8, the corona discharge treatment effect will be insufficient and a high level of adhesion will occur. I can't get sex. In this sense, the present invention adopts the treatment method shown in the figure, and also when the (N/C) ratio is 3 or more, [Δ(O/C)/Δ(N/
It is essential to control the processing conditions so that C)] is 1.8 or less. The present invention is roughly configured as described above, and the corona discharge treatment conditions are defined, and the treatment effect is determined from the amount of change in the (O/C) ratio and (N/C) ratio of the surface layer before and after treatment. By constantly monitoring the information, it has become possible to reliably obtain polyolefin molded products with excellent adhesion to various materials. Next, an experimental example will be shown. The method for evaluating surface characteristics adopted in the examples is as follows. (1) Haze: Measured according to JIS-K-6714 (2) Printing ink adhesive strength Red and white printing was performed using a gravure printing machine using a commercially available cellophane printing ink. After printing, the prints were simultaneously dried in a conventional manner and subjected to tape peeling tests, kneading tests, and scratch tests using commercially available cellophane tape (manufactured by Nichiban Co., Ltd.). ○B Tape peeling test evaluation criteria 5: No peeling at all 4: Ink peeling area is less than about 5% 3: Ink peeling area 5-10% 2: Ink peeling area 10-50% 1: Ink peeling area 50% or more○ B. Massage test (knead the same area 5 times and judge with the naked eye how much ink has fallen off) 5: No ink falling off at all 4: Slight falling on the line, but no practical problem 3: Falling off in several places on the wrinkled line 2: Many places fell off on the wrinkled line 1: Many fell off along the line, also in the width direction ○C Scratching test Place the printed matter on hard paper and scratch the printed area to check the state of ink falling off. (3) Lamination strength After printing with cellophane ink, coat with polyethyleneimine, dry and then laminate with low density polyethylene at 290℃ using melt extrusion method to a thickness of 30μm. After aging for 24 hours, the film and polyethylene layer were peeled off and the adhesive strength was measured. The peeling conditions are as follows:
Peel 180 degrees at a speed of 200 mm/min. (4) Other adhesive properties Examine the vapor deposition properties of aluminum and the adhesion properties with vinylidene chloride resin using the same method as in (2). (5) Oxygen concentration on the film surface An atmospheric gas suction sensor was attached on the film surface, and the oxygen concentration at a position within 100 μm above the film surface was measured. (6) ESCA analysis value (N/C) ratio and [O/C] by ESCA method
Ratio: Using an ESCA spectrometer ES-200 model (manufactured by Kokusai Denki Co., Ltd.), we measured the carbon content on the film surface.
Calculate the ratio of the integrated intensity obtained from the peak corresponding to the binding energy of organic nitrogen from the ls orbital spectrum, calculate the number of nitrogen per 100 carbons based on the integral ratio, and calculate this value (N/C). It is defined and expressed as a ratio. The ratio of carbon to oxygen on the film surface was similarly expressed as the number of oxygen per 100 carbon atoms as the (O/C) ratio. Note that the (N/C) ratio and (O/C) ratio in this specification are all based on this definition. Experimental example 1 Isotactic polypropylene (MI=4.0)
A biaxially stretched film with a thickness of 20 μm was obtained using a conventional method, and this was used as the film to be treated. This film was subjected to corona discharge treatment while being sprayed with nitrogen gas having the oxygen content shown in Table 1.
The processing power was 4000 joules/m ² , and for comparison, the corona discharge treatment was also carried out in the same manner in which the atmospheric atmosphere and the processing atmosphere were simply replaced with nitrogen gas. The processing speed was 20 m/min in both cases.

[Table] (O/
Table 2 shows the values of the C) ratio and (N/C) ratio before and after the treatment, and the results of the adhesion test of each film obtained. Furthermore, the adhesive strength of the laminated surface of the film printed on the film, laminated with polyethylene (PE), and heated and pressed for 2 seconds using a hot plate at 130° C. was examined, and the results shown in Table 3 were obtained.

【table】

【table】

[Table] As is clear from Tables 1 to 3, not only when the corona discharge treatment is performed in the air (No. 1), but also when the discharge system is simply replaced with nitrogen gas (No. 1).
2, 3, 4) [Δ(O/C)/Δ(N/C)] cannot be suppressed to a low level, resulting in insufficient adhesion. In particular, for Nos. 3 and 4, the (N/C) ratio after treatment, which is the requirement 1 in the present invention, is satisfied, but the [Δ(O/C)/Δ(N/C)] Because the value is too large, sufficient adhesion cannot be obtained. On the other hand, even when the oxygen concentration is approximated to the conventional example (No. 2, 3), if this is sprayed onto the discharge treated surface (Example:
No. 5, 6), the (N/C) ratio after treatment effectively increases and [Δ(O/C)/Δ(N/C)] also increases to 1.8.
It shows excellent adhesion to all the materials used. As is clear from these results, in corona discharge treatment, it is insufficient to grasp the O ₂ concentration of the entire discharge atmosphere, and a high nitrogen concentration gas is actively sprayed onto the surface to be treated to create an accompanying air layer. of the discharge surface by destroying and diffusing the
Reducing O ₂ concentration is a critical requirement. Although Comparative Example Film No. 4 seems to be practical, it was confirmed that the level of adhesiveness was low overall, and that the adhesiveness to cellophane was extremely reduced especially by heat treatment. Experimental Example 2 A biaxially oriented polypropylene film (Pylene film manufactured by Toyobo Co., Ltd.) was used as the film to be treated.
OT, P-2061, 20 μm), and corona discharge treatment was performed under the conditions shown in Table 4. Experiment No.7
-12, the nitrogen gas amount was constant at 8 m ³ /hr·m per 1 m film width, and the gas spraying speed in the example was 1.8 m/sec. Also experiment No. 18~
16 is an example in which the oxygen concentration on the film surface on the film discharge side was adjusted by changing the gas supply amount, but in the case of a method of simply blowing gas into the processing equipment (comparative examples: No. 13 and 14), Compared to the method of spraying gas onto the film surface (Examples: Nos. 14 and 15), the same oxygen concentration cannot be obtained unless 3 to 8 times the amount of gas is supplied. Table 5 shows the adhesiveness of each film obtained above. Furthermore, as a method for blowing gas into the processing equipment (comparative examples: No. 17 to 20), the gas supply amount is made equal (comparative examples: No. 17 and 18), and the gas used is oxygen gas (comparison). Example: Table 6 shows the relationship between oxygen concentration and ESCA analysis values for Nos. 19 and 20). In the present invention, since the gas atmosphere at the film interface is important for substantially effective treatment, the O ₂ concentration on the film surface was measured by the method described above and is also listed in Table 6.

【table】

【table】

【table】

[Table] As is clear from Tables 4 and 5, even when the processing speed, processing power, and O ₂ concentration in the atmosphere are set to be approximately the same, high nitrogen concentration gas is simply blown into the equipment. (Comparative example: No. 7 to 9 and
13, 14), an accompanying air layer is formed on the film surface and the processing efficiency decreases, especially when [Δ(O/C)/
Δ(N/C)] cannot be suppressed to a low level,
Although adhesion cannot be sufficiently increased, spraying high nitrogen concentration gas on the film surface (Example:
10-12 and 15, 16), the accompanying air layer is destroyed and removed by the jet flow, increasing the treatment efficiency;
(O/C)/Δ(N/C)] can be made to an extremely low level, and adhesion to various materials is dramatically improved. Furthermore, as shown in Table 6, simply blowing high nitrogen concentration gas into the processing apparatus was insufficient to reduce the O ₂ concentration on the film surface, as shown in Nos. 13, 14, 17, and 18.
Also, the [Δ(O/C)/Δ(N/C)] ratio and the post-treatment (N/C) ratio did not reach their targets, and good adhesion could not be obtained. Also into the processing equipment
Blow in O ₂ to make the O ₂ concentration on the film surface higher than the air composition (i.e., make the nitrogen concentration lower than the air composition)
No. 19, 20) did not give satisfactory results either.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram showing the implementation status of the present invention, Figure 2
The figure is a sketch diagram illustrating the discharge side electrode used in the present invention, FIG. 3 is an explanatory diagram showing the state of destruction of the accompanying air layer, and FIG. 4 is an explanatory diagram showing an example of the electrode cover. 1...metal drum, 2...electrode cover, 3...
Discharge side electrode, 5... gas jet port, 6... film.

Claims (1)

[Scope of Claims] 1. A polyolefin molded product obtained by performing corona discharge treatment while running through a corona discharge treatment device having at least one pair of electrodes facing each other, which A gas having a higher nitrogen concentration than the air composition is sprayed along the side wall surface of the discharge side electrode or from the bottom surface toward the corona discharge treatment surface of the polyolefin molded product at a speed of 1% or more of the conveyance speed of the polyolefin molded product. In addition to destroying and dispersing the entrained air layer, the (O/C) ratio and (N/C) ratio in the thin layer within 100 Å from the surface of the polyolefin molded article are
C) The ratio of the amount of change in ratio before and after corona discharge treatment [Δ(O/C)/Δ(N/C)] is set to 1.8 or less,
A highly adhesive polyolefin molded article, characterized in that a thin layer within 100 Å of the surface of the molded article has an (N/C) ratio of 3 or more after corona discharge treatment. However, (O/C) ratio: Oxygen per 100 carbons (N/C) ratio: Nitrogen per 100 carbons