JPS6034970B2 - Method for treating the surface of propylene polymer moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [1] Object of the Invention The present invention relates to a method for treating the surface of a molded article of a propylene polymer.

More specifically, the thickness is 5. A molded product of propylene-based polymer below 25% at a temperature of 50 to 100 oo
Propylene treated by corona discharge treatment in a gas atmosphere having an oxygen concentration of vol% or more so that the surface layer of the molded product has at least 1 solid oxygen atom per 100 carbon atoms. The present invention relates to a method for treating the surface of a molded product made of a propylene polymer, and the purpose of this method is to provide a molded product (for example, a film) made of a propylene polymer that has improved printability with printing ink for cellophane. That is. [B] Background of the Invention Propylene polymers (propylene homopolymers, propylene-based copolymers) are hydrophobic monsters with extremely low critical surface tension. It is well known that treatments such as painting, printing, metal plating and adhesion with other materials are extremely difficult.

It has been proposed that the polymer be subjected to the following improvement methods before these treatments. '1- The molded product of propylene polymer has ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer on one side,
A method in which a polymer such as a polyethyleneimine polymer or a -propylene copolymer is coated, and a process such as printing is performed through a coating layer made of a polar or non-polar polymeric substance [hereinafter referred to as ``Processing method '1}''].

■ A method in which an antistatic agent such as a fatty acid monoglyceride, a quaternary ammonium compound, and a betaine type compound is added to a propylene polymer in advance, and a molded product of the polymer containing the antistatic agent is subjected to corona discharge treatment [hereinafter referred to as the "treatment method"] '21']

'3} A method of subjecting a molded product of a propylene polymer to a corona discharge treatment in an atmosphere such as nitrogen, carbon dioxide gas, or air under heating [hereinafter referred to as "treatment method {3'"].

However, in the case of treatment method (1'), the polymer coated on the surface of the propylene-based polymer molded product is a polar or non-magnetic soft polymer material, so the coated molded product has blocking properties and surface smoothness. Not only are properties inferior, but also a decrease in transparency due to the combination of different types of polymers cannot be avoided.

In addition, in treatment method ① and treatment method '31, chemical reactions and physical sludge formation on the surface of the molded product are unlikely to occur, so the effects on the adhesion and adhesion of printing ink and the plating properties of metals are not necessarily satisfactory. Not only is it not a kimono, but especially when processing in nitrogen or carbon dioxide gas, corona treatment is performed in an atmosphere almost exclusively of these gases (with almost no other gases present).
Since it is necessary to carry out the treatment in a controlled manner, it is often difficult to apply this treatment method industrially, regardless of whether it is used in a laboratory.

[m] Structure of the Invention The present inventors have conducted various searches to improve the above-mentioned drawbacks due to the processing method [1 stitch 3} 1, and as a result, the thickness 5.
A molded article of propylene polymer below the ribs is subjected to corona discharge treatment in a gas atmosphere with a temperature of 50 to 100 pm, and 2) an oxygen concentration of 2% by volume or more to remove carbon from the surface area of the molded article. The inventors have discovered that a surface treated product having at least 10 oxygen atoms compared to 10 atoms has improved printability with printing ink for cellophane, and has thus arrived at the present invention.

[W] Effects of the Invention The surface-treated product obtained by the present invention not only improves the printability of printing ink for cellophane, but also has the following effects.

'1} Gas permeability, metal deposition properties and thermal adhesion properties are improved. ■ Improved compatibility with paints.

[V] Detailed description of the invention Molded article of propylene polymer The thickness of the molded article of propylene polymer used in the present invention is 5.0 mm or less.

The lower limit is not particularly limited, but is generally 0.005 ribs (5 microns). {1} Propylene-based polymers Propylene-based polymers are propylene homopolymers, propylene and ethylene, or Q containing at most 6 carbon atoms.
-olefins (e.g. butene-1, hexene-1)
Examples include copolymers with

The copolymer proportion of these ethylene or Q-olefins is generally at most 4% by weight and 2% by weight.
The following is preferred, particularly 1% by weight or less.

In addition, these propylene polymers are essentially stereoregular, and the melt properties of these propylene polymers are
Flow Index (hereinafter referred to as "MFI", JIS)
(measured by K-67 spots) is generally 0.1 to 30 minutes, preferably 0.5 to 10 minutes. In the present invention, the propylene polymer is used in advance as a stabilizer against oxygen, heat, ozone, and light, a filler, an antistatic agent, a lubricant, and a processability agent that are normally used in propylene polymers depending on the purpose of the molded product. Additives such as improvers may be added (blended) for use.

Furthermore, ethylene copolymers such as ethylene homopolymers, ethylene monovinyl acetate copolymers, copolymers of ethylene with acrylic esters or methacrylic esters, and copolymers of ethylene with other Q-olefins; - Rubbery materials such as propylene rubber, butadiene rubber, and styrene-butadiene rubber may be blended. It goes without saying that these additives, ethylene homopolymer, ethylene copolymer, and rubber-like material must be blended within a range that does not essentially impair the properties of the propylene polymer used in the present invention. ■ Manufacture of molded products Typical examples of molded products used in the present invention include unstretched films obtained from propylene polymers using a T-die extruder, and
Examples include films obtained by monotactically or biaxially stretching at a temperature of .

Further examples include unstretched and stretched films obtained by inflation molding a propylene polymer. [B} Atmosphere ○} Processing temperature In the atmosphere for corona discharge treatment in the present invention, the processing temperature is 50 to 10 and ○, preferably 55 to 9,500, and particularly preferably 60 to 9,000.

If the treatment temperature is below 50 qo, the treatment effect will be poor. On the other hand, if it exceeds 100°, not only will printability and other effects be reduced, but the molded product will shrink and whiten significantly, and its surface smoothness and transparency will be impaired. In order to obtain this treatment temperature, there are two methods: directly heating the molded product before corona discharge treatment using a heating device such as an infrared heater or quartz tube heater, or heating it using a heating guide roll. do it.

Further, after the corona discharge treatment, the treated molded product is preferably cooled by air cooling or by using a cooling guide roll, depending on the case.

t2) Oxygen Concentration Furthermore, the gas atmosphere has an oxygen concentration of 2% by volume or more, preferably 3% by volume or more, and particularly preferably 30-9% by iron volume.

In order to adjust the oxygen concentration to this level, the corona discharge treatment section is essentially carried out in a closed atmosphere.

As an example of adjusting to this atmosphere, after reducing the pressure in the corona discharge treatment area, oxygen gas is introduced into the system, and other gases (e.g., nitrogen gas, air helium gas, argon gas) are introduced into the system.
The oxygen concentration may be adjusted to the above oxygen concentration.

{C} Corona discharge treatment Corona discharge treatment is a device generally used for corona discharge treatment of molded articles (e.g., films) of thermoplastic resins such as ethylene polymers and propylene polymers. You can use
No. 442, No. 39-21137, No. 40-12383
No. 43-631, see specification).

When a film is used as a molded article through this corona discharge treatment, the film processing speed (take-off speed) is generally 10 to 200/min.

Electrode gap (scale p) interval (gap between main electrode and counter electrode)
is generally 0.2~5cm, and the discharge voltage is 1000~
It is 50,000 volts. Furthermore, the oscillation frequency is 3 to 1
It is 50 kilohel (K ratio). Even when a molded product other than a film is used, the corona discharge treatment may be performed under the same conditions as above. Although the theoretical background of the present invention is not necessarily clear, surface infrared absorption spectrum analysis of the corona-treated surface revealed absorption of polar functional groups such as carbonyl groups and hydroxyl groups.

From this phenomenon, an oxidation reaction of the propylene polymer occurred in a very thin layer on the corona-treated surface, and the produced >C=○, 1C
It is thought that polar functional groups such as OO, -CH◯, and -OH are generated. Furthermore, X-ray photoelectron spectrum analysis (commonly known as ESCA) of the corona-treated surface was performed.

The measurements were carried out using MgK2 rays as the X-ray source, the measured attenuation was IKcps', and the degree of vacuum was 10 orr or less. The number of oxygen atoms per carbon atom ION in the surface layer of the treated product obtained according to the present invention as measured by the above method is preferably 1 or more, and preferably less than 3.
If the number of oxygen atoms per 10 M of carbon atoms in the surface layer is less than the number IN, there will be little effect on printability etc. due to the small number of polar functional groups due to oxidation reaction. On the other hand, it was found that in the case of hardness of 3 or higher, the effect on printability etc. is reduced. This is probably due to the formation of a degraded layer on the surface due to excessive oxidation reaction occurring on the surface. In addition, in the present invention, “
"Surface layer" is the range in which the above-mentioned X-ray photoelectron spectrum analysis can be performed, and is generally 50 to 100 A below the surface.
This refers to layers up to 0 (Angstrom).

Furthermore, since the treatment temperature according to the present invention is relatively high as described above, electron bombardment during corona discharge treatment causes
It is thought that the surface texture of the propylene polymer is progressing.

As described above, the treated product obtained by the present invention not only has excellent printability with printing ink for cellophane, but also has no blocking between the treated and non-treated surfaces and has excellent transparency.

Furthermore, the molded product obtained by the present invention can also be used for coating with materials other than printing ink, adhesion, and metal plating. [W] Examples and Comparative Examples The present invention will be further explained in detail with reference to Examples below.

In addition, in the examples and comparative examples, the wetting tension is JIS
Measured according to K-6768.

In addition, the printability was tested using cellophane printing ink (manufactured by Toyo Ink Co., Ltd., product name: CC) on corona-treated polypropylene film.
After applying ST), the temperature and humidity of 23○ are 65
% for 2 hours. Next, a commercially available cellophane tape (manufactured by Nichiban Co., Ltd.) is applied to the coated surface using finger pressure, and then the cellophane tape is peeled off.The ratio of the area of printing ink remaining after peeling to the total area is expressed in %. Furthermore, the blocking index (blocking property) was determined by overlapping the corona-treated side and the non-corona-treated polypropylene film after corona treatment, and leaving the film at a temperature of 50 degrees Celsius for 2 hours under a load of 100 days/carp. After standing, the degree of peeling of the two films was qualitatively expressed in the following five ranks. Rank Peeling (blocking) condition 1 No blocking 2 Almost no blocking 3 Slight blocking 4 Somewhat reblocking 5 No peeling Also, transparency was determined according to ASTM DIO03-61 using a transmittance measuring device (manufactured by Nippon Seimitsu Kogaku Co., Ltd.) The evaluation was made by measuring the light transmittance of the film and calculating the haze using the following formula.

Haze (%): Obi-kari.

(However, Td represents diffuse transmittance and Tt represents total transmittance).

Furthermore, smoothness was determined visually. In each example and comparative example, propylene homopolymer (MF 12.0 /
10 minutes), the thickness is 0.025.
I made the side film. This film was subjected to corona discharge using the apparatus shown in FIG. In Figure 1,
1 is an unwider, and the above film 1 is
2 is wrapped. Film 20 from this unwider
It is guided to a heating roll 2 and a heating roll 3 whose surfaces are heated by steam at a speed of 100 m/min, and then to a processing roll 9. The surface temperature of the treatment roll was adjusted as shown in Table 1. After the film has been treated with corona discharge by electrode 10 (set by generator 11 (output voltage 150 volts 12 amperes))
The distance between the electrode and the film is 1. Q factory), the winder 6 is cooled by the cooling roll 4 and the cooling roll 5.
It is wound up. Furthermore, 13 is sealed,
Oxygen gas from a nitrogen cylinder and an oxygen cylinder is introduced into the sealing device 13 through the supply port 7 while being regulated to the oxygen gas shown in Table 1, and is discharged from the gas discharge port 8. The corona discharge machine treatment was performed using an all-transistor type corona discharge device (manufactured by Pillar, model 2.1 KVA, power input 3-phase 200 volts, oscillation frequency 9.6 kilohertz, discharge voltage 9000 volts). Examples 1 to 5 and Comparative Examples 1 to 3 Films were subjected to corona discharge treatment under the treatment temperature (temperature of the surface of the treatment roll 9) and the oxygen concentration in the sealing vessel 13 (the rest is the nitrogen concentration) shown in Table 1. I did it.

Table 1 shows the wetting tension, printability, blocking index, haze, and number of oxygen atoms relative to carbon atom ION hardness in the surface layer of the film for each of the treated films. Table 1 1) Impossible to measure more than 54 tines/skin 2) For 100 carbon atoms in the surface layer Example 6, Comparative Example 4 Instead of the propylene homopolymer film used in Example 2, the same Thick propylene-ethylene random copolymer (ethylene content 2.5% by weight, h cape 11
．． Example 2, except that a film of 0 pm/1 pm) was used.
Corona discharge treatment was performed under the same conditions.

The number of oxygen atoms in the treated film surface layer was 28 compared to the carbon atoms in the ION solids. In addition, the wet tension of this film is 54 dynes/pressure or more, and the printability is 100
Met. Further, the blocking index was 2 and the haze was 3.5% (Example 6). In addition, corona discharge treatment was performed under the same conditions as in Comparative Example 1, except that the propylene-ethylene random copolymer film used in Example 6 was used instead of the propylene homopolymer used in Comparative Example 1. .

The number of oxygen atoms per 100 carbon atoms in the surface layer of the treated film was 8. Further, the wet tension of this film was 46 dynes/dyne/dyne, and the printability was 55. Furthermore, the blocking index is 2 and the haze is 33.
% (Comparative Example 4). From the above Examples and Comparative Examples, when the processing temperature is 50°C or lower, the printability is poor and the 100%
If the temperature is above 0:00, the printing properties are excellent, but the blocking properties and transparency (haze) of the processed film are poor.

Furthermore, if the oxygen concentration is less than 2%, printability is poor.
Therefore, it is clear that a treated product with excellent printability, transparency and blocking properties cannot be obtained unless the treatment is performed at a treatment temperature of 50 to 100 qo and in an atmosphere with an oxygen concentration of 23% by volume.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the arrangement used for corona discharge treatment in each of the Examples and Comparative Examples. Groove diagram

Claims (1)

[Claims] 1 A propylene polymer molded product with a thickness of 5.0 mm or less is subjected to corona discharge treatment at a temperature of 50 to 100°C in a gas atmosphere having an oxygen concentration of 25% by volume or more, and carbon is removed in the surface layer of the molded product. A method for treating the surface of a propylene-based polymer molded article, which comprises treating the surface of a propylene-based polymer molded article to have 10 or more and less than 30 oxygen atoms per 100 atoms.