JPS59147027A - Surface treatment of molded article of resin - Google Patents

Abstract

PURPOSE:To carry out surface treatment for improving printability, adhesiveness, coating performance, etc. of molded article of a specific propylene-ethylene block copolymer, by irradiating the surface of the molded article with ultraviolet rays from a low-pressure mecury lamp having specified wavelength peaks. CONSTITUTION:The surface of a molded article of a propylene-ethylene block copolymer having >=2wt%, preferably >=4wt% ethylene content, >=0.2g/10min melt flow index, a ratio (I735/I720) of absorbance (I720) at 720cm<-1> melt infrared absorption spectrum at 140 deg.C to absorbance (I735) at 735cm<-1> of <=0.8, preferably <=0.7 is irradiated with ultraviolet rays from a low-pressure mercury lamp having peaks at 1849Angstrom and 2537Angstrom wavelength at preferably 80-6,000colon.volt/ cm<2> intensity of irradiation, to carry out surface treatment of the molded article of the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION CI) Object of the Invention The present invention relates to a method for surface treatment of molded articles of propylene-ethylene block copolymers. More specifically, the ethylene content is at least 2% by weight, the melt flow index is 0.2 g/10 minutes or more, and 140
The absorbance at 720 cm (I720) and the absorbance at 735 J-” (Ir3) of the melt infrared absorption spectrum at °C
Ultraviolet rays from a low-pressure mercury lamp having wavelength peaks at 1849 angstroms and 2537 angstroms were applied to the surface of a molded product of a propylene-ethylene block copolymer having a ratio (I tsi /I 72°9 of 0.8 or less). The present invention relates to a method for surface treatment of a resin molded article characterized by irradiation, which improves the printability of the molded article,
The purpose is to improve suitability for secondary processing such as adhesion and paintability.

BACKGROUND OF THE INVENTION As is well known, olefin resins not only have excellent moldability but also have good properties such as mechanical strength, heat resistance, solvent resistance, and chemical resistance, so they are widely manufactured industrially. It is used in many fields as a general-purpose resin. Because of these properties, olefin resins have recently been developed for use in automobile parts such as bumpers, instrument panels, front grills, fenders, and headlight cases. However, since olefin resins do not have polar groups in their molecules (so-called non-polar), they are chemically extremely inactive polymeric substances. Furthermore, it not only has high crystallinity but also extremely low solubility in solvents, so when used in fields such as painting and adhesion, it has low paintability and adhesiveness.

As mentioned above, although olefin resins have excellent moldability and the above-mentioned properties, olefin resins are used in fields where good adhesion and paintability are required (for example, automobile parts, home appliance parts). There were naturally limitations to the use of resins.

In order to solve the problems of adhesion and paintability of olefin resins, various methods as described below have been proposed for quite some time.

(a) A method in which an olefin resin or a molded product thereof is surface-treated from the outside and modified by a physical or chemical method (hereinafter referred to as "modification method").

(b) A method of adding other polymeric substances or additives to the olefin resin (hereinafter referred to as "addition method").

Hereinafter, among these methods, the modification method will be explained in more detail and problems will be described.

This method includes ``flame treatment method, plasma treatment method, ozone treatment method, corona discharge treatment method, and irradiation treatment method using ultraviolet rays or electron beams'' [hereinafter referred to as ``denaturation method (a)''.
] and "method of treatment using a mixed solution of chromic acid and mineral acids such as concentrated sulfuric acid, and treatment using a compound containing a polar group in the olefin resin or its molded product in the presence or absence of a crosslinking agent." [hereinafter referred to as "modification method (b)"]].

These modification methods provide chemically active sites rich in polar groups to the surface of the olefin resin or molded product thereof, thereby making it possible to physically roughen the surface. As a result, it is thought that the effects of improved paintability and adhesiveness can be obtained.

However, in order to carry out this modification method (1), the shape of the molded object to be treated must be significantly limited, and furthermore, if left after treatment, the treatment effect not only deteriorates significantly over time, but also the In many cases, the degree of oxidation is not always sufficient.Furthermore, it has disadvantages such as being economically disadvantageous because it requires various expensive processing equipment.

In addition, among the modification methods (b), the treatment method using mineral acids not only tends to cause the chemicals used to be a source of pollution, but also requires complicated post-treatment steps such as neutralization, water washing, and drying. be. Furthermore, chemical processing methods such as grafting require a drying process, and furthermore, not only do detailed considerations such as monomer application and grafting atmosphere require a relatively long grafting reaction time, but the grafting reaction time is relatively long. . Therefore, it has drawbacks such as not being suitable for continuous production.

Furthermore, the addition method includes a so-called resin blend method in which a rubber substance and/or a resin containing a polar group is blended with an olefin resin, and a filler (for example, calcium carbonate, barium sulfate, talc, clay).
Examples of methods of addition include: However, even if the composition obtained by this addition method can improve adhesion, paintability, etc., it has drawbacks such as decreased mechanical strength, heat resistance, etc., and further reduced processability. .

As mentioned above, both the modification method and the addition method can improve paintability and adhesion to some extent, but each method has various drawbacks, so there are no satisfactory improvement methods. It's hard to say.

Furthermore, as a method for imparting paintability and adhesion to the surface of olefin-based polymer molded products, polyolefins are prepared by graft-polymerizing chlorinated polypropylene or maleic anhydride onto the surface of the molded product before applying paint or adhesive. A method has been developed to apply a primer whose main ingredients are:

However, the method of applying a primer increases the cost by adding one step of coating or adhesion.

(]lD Structure of the Invention) From the above, the present inventors have conducted various searches to obtain molded products of olefin resin that have excellent printability, adhesiveness, and paintability despite these drawbacks. As a result, the ethylene content was at least 2% by weight, and the melt flow index (measured according to JIS K-6758 at a temperature of 230°C and a load of 2.16 K9, hereinafter referred to as 1-MFIJ) was 0. .2, 9/10
minutes or more, and 14. Absorbance of 720Crn and 735d' of melt infrared absorption spectrum at O'c
-' absorbance (l735) ratio ('735/l72
A surface treatment of a resin molded article, characterized in that the surface of a molded article of a propylene-ethylene block copolymer having a 0 ) of 0 or less is irradiated with ultraviolet rays from a low-pressure mercury run having wavelength peaks at 1849 angstroms and 2537 angstroms. The inventors have now discovered that a molded article of propylene-ethylene block copolymer which does not have the above-mentioned drawbacks and has excellent printability, adhesion and paintability can be obtained by this method, and has thus arrived at the present invention.

■ Effects of the Invention The molded product obtained by the present invention and irradiated with ultraviolet rays, including its manufacturing method, exhibits the following effects.

(1) Printability, adhesiveness and paintability are superior to molded products obtained by the above modification method.

(2) There is no pollution source due to the chemicals generated in the modification method (b), and furthermore, there is no need for post-treatment steps, and the treatment can be carried out continuously using inexpensive equipment.

(3) There is no change over time after the treatment (/'l0 (4) The treatment can be carried out at normal temperature and pressure, and by devising the equipment, the shape of the object to be treated can be selected to a certain extent. can do.

(5) Wide selection of paints, adhesives, printing inks, etc.

V Detailed description of the invention (A) Propylene-ethylene block copolymer The ethylene content of the propylene-ethylene block copolymer (A) used in the present invention is at least 2 weights, preferably 3 weights or more. , especially those of 4 weight class or more are suitable. If the ethylene content of the block copolymer is less than 2% by weight, the peel strength of the resulting printed materials, adhesives, and painted products will be low. Further, the MFI is 0.2g710 minutes or more, preferably 0.39710 minutes or more, and particularly preferably 0.4.9710 minutes or more. If a block copolymer having an MFI of less than 0.29710 minutes is used, a good molded product cannot be obtained. Furthermore, the absorbance ratio (I 73v /I , □.) of the melt infrared spectrum at 135° C. of this block copolymer is 0.8 or less, preferably 075 or less, and particularly preferably 0.7 or less. When the absorbance ratio of the propylene-ethylene block copolymer exceeds 08, the peel strength of the resulting printed matter, adhesive, and painted product will be low.

(B) Ultraviolet irradiation method In order to carry out the ultraviolet irradiation of the present invention, an ultraviolet irradiation device having peaks at 1849 angstroms and 2537 angstroms is used. 184
A wavelength of 9 angstroms is effective for generating ozone for chemically modifying the propylene-ethylene block copolymer used, while a wavelength of 2537 angstroms is effective for generating ozone for chemically modifying the propylene-ethylene block copolymer used, while a wavelength of 2537 angstroms is effective for generating ozone for chemically modifying the propylene-ethylene block copolymer used. H
It appears to be effective for cleaving groups and C-C groups.

If an irradiation device (eg, a high-pressure mercury lamp) that does not emit ultraviolet light at a wavelength of 1849 angstroms is used, the effect described above is extremely small. Since the wavelength of 1849 angstroms is a short wavelength, the attenuation in the processing atmosphere is significant and the molecular cleavage of the propylene-ethylene block copolymer is insufficient, so a wavelength of 2537 angstroms is absolutely necessary.

The intensity of ultraviolet rays to the irradiated surface is preferably 80 to 6000 coulomb volts/crn2, particularly 220 to 2200 coulomb volts/crn2.
Coulomb volt/crn2 is preferred.

However, the intensity of the ultraviolet rays on the irradiated surface is 80 coulomb volts/
If irradiation is performed before reaching 'Crn2, the above-mentioned treatment effect will be poor. On the other hand, 6000 coulomb pol)/cm
If irradiation exceeds 1, a brittle layer will be formed on the surface of the object, which is undesirable. From the above, it is necessary to appropriately select the energy of the ultraviolet generator, the distance from the generator to the irradiation surface, etc. so that the irradiation surface of the object to be treated falls within the intensity range of the ultraviolet rays described above.

(C) When carrying out the ultraviolet irradiation of the present invention, such as manufacturing a molded article, the propylene-ethylene block copolymer is directly molded into a molded article by the molding method described below.

In this case, the propylene-ethylene block copolymer contains light (ultraviolet), heat and ozone stabilizers, flame retardants, lubricants, etc. used in the field of propylene resins.
Additives such as fillers, processability modifiers, antistatic agents, colorants and electrical property modifiers may also be included.

In producing the molded product of the present invention, when using the above additives, mixers such as mixing rolls, kneaders, panburr mixers, and extruders commonly used in the field of propylene resins are used. A common method is to melt and knead the mixture. Before this melt-kneading, these ingredients may be tri-blended in advance using a mixer such as a Henschel mixer or a ribbon blender, and the resulting mixture may be melt-kneaded.

The composition (compound) obtained in the above manner is molded into a film, plate, pipe, or container by molding methods such as injection molding, extrusion molding, and blow molding in the field of propylene polymers. , formed into a rod-like shape.

(D) Method of use The treated product obtained by the present invention has an irradiation surface of 10H.
Because it has functional groups such as -COOH and -COOH groups, it is easy to coat with paints that have coating properties, compatibility, or reactivity with these functional groups, adhere with adhesive properties, and print on the irradiated surface. Moreover, it can be implemented robustly. These coating, adhesion, and printing methods are not special methods, and commonly used methods may be applied. Paints, adhesives, and inks containing urethane resins, epoxy resins, acrylic resins, phenol resins, and polyester resins as main components are advantageous in view of the relationship between the above-mentioned functionality and coating properties, compatibility, and reactivity.

(2) Examples and Comparative Examples The present invention will now be explained in more detail with reference to Examples.

In addition, in the Examples and Comparative Examples, the tensile peel strength was determined by cutting the coated sample into 1 cm width after leaving it for 24 hours. Using Tensilon (all-purpose type), the resin (propylene-ethylene block copolymer) was fixed to the upper and lower chucks, and the strength was measured when it was peeled off at a speed of 50 inches, ..., 17 minutes. .

In addition, the propylene used in the examples and comparative examples
Table 1 shows the ethylene content, MFI, and absorbance ratio (■qs5./l720) of the ethylene block copolymer.

Table 1 Examples 1 to 3, Comparative Examples 1 to 6 The above globylene block copolymers were molded using a 5 oz injection molding machine (manufactured by Toshiba Machine Co., Ltd., trade name: 1S-80), and the resin temperature was 230°C. ℃, the mold temperature was 40℃ and the injection specimen (
It was molded to a thickness of 2 trrmll 0 crn x 10 cm). The obtained injection specimen was irradiated with UV (ultraviolet light) using a UV lamp (manufactured by Ushio Inc., trade name: Type UVR40, 40 Watt). In addition, in Comparative Example 6, a high-pressure mercury lamp (manufactured by Tokyo Shibaura Electric Co., Ltd., trade name Hl) was used.
In Comparative Example 1, no irradiation was performed (the distance, time and intensity of UV irradiation are shown in Table 2).

Apply urethane paint (manufactured by Nippon B Chemical Co., Ltd., trade name R-257) to each specimen thus obtained using a spray gun at a pressure of 4 Ky/cm2 to a film thickness of 60 microns on the surface. Sprayed evenly. After being left at room temperature for 10 minutes, it was heated and dried at 80° C. for 30 minutes. Thereafter, after being left at room temperature for 48 hours, the peel strength of the coating film was measured.

The results are shown in Table 2.

Table 2 Patent applicant: Shuwa Denko Co., Ltd.

Claims (1)

[Claims] The ethylene content is at least 2% by weight, the melt flow index is O,'2 g/1o min or more, and the melt infrared absorption spectrum at 140 °C is 7.
Absorbance CI at 20cm? 20) and 735 crn, the surface of a molded article of a propylene-ethylene block copolymer is irradiated with ultraviolet rays from a low-pressure mercury lamp having wavelength peaks at 1849 angstroms and 2537 angstroms. Method.