CN109849547B

CN109849547B - Rubber flexible printing engraving plate and manufacturing method thereof

Info

Publication number: CN109849547B
Application number: CN201910074024.4A
Authority: CN
Inventors: 徐毛清; 徐益良; 高杰亮; 俞辉
Original assignee: Jiangsu Kangpu Printing Technology Co ltd
Current assignee: Jiangsu Commscope Printing Technology Co ltd; Shanghai Haomi New Material Technology Co ltd
Priority date: 2019-01-25
Filing date: 2019-01-25
Publication date: 2021-03-05
Anticipated expiration: 2039-01-25
Also published as: CN109849547A

Abstract

The invention provides a rubber flexible engraving plate and a manufacturing method thereof, wherein the rubber flexible engraving plate is of a three-layer structure and comprises an engraving layer (1), an adhesive layer (2) and a backing layer (3), and the engraving layer (1), the adhesive layer (2) and the backing layer (3) are sequentially arranged from top to bottom. The rubber flexible engraving plate can be directly engraved and formed by laser, the manufacturing mode of the flexible resin plate is changed, industrial hazardous waste cannot be generated in the plate making process of the rubber flexible engraving plate, and the reproduction performance of mesh points below 5% in the printing process is improved.

Description

Rubber flexible printing engraving plate and manufacturing method thereof

Technical Field

The invention belongs to the technical field of printing, particularly belongs to the technical field of flexible printing engraving plate processing, and relates to a rubber flexible printing engraving plate and a manufacturing method thereof, in particular to a rubber flexible printing engraving plate capable of being directly engraved and formed by laser, which can replace a flexible printing resin plate.

Background

At present, printing plates used for domestic flexible printing generally adopt resin plates made of photosensitive resin materials, and the structure of the printing plates is a black film layer, a photosensitive resin layer and a base layer from top to bottom. The plate making mode of the printing plate is that the image-text part is formed by photo-curing photosensitive resin, then the redundant part of the resin is washed away by using a chemical solvent, and then the drying and the de-sticking treatment are carried out in sequence.

CN108349286A discloses an offset printing plate, wherein the offset printing plate comprises: a cylindrical printing plate base material; a silicone resin layer formed on the printing plate base material; and a resist pattern portion formed on the silicone layer, the silicone layer being a non-picture line portion, the resist pattern portion being a picture line portion.

CN101466555A discloses a method for manufacturing a resin-containing screen printing mask, which is a method for manufacturing a resin-containing screen printing mask in which a resin layer having openings at substantially the same positions as the openings is provided on one main surface of a screen printing mask having openings, comprising the steps of: and a step of forming an opening in the resin layer by removing a part of the resin layer located at substantially the same position as the opening of the screen printing mask in a self-aligning manner.

CN107663285A discloses a flexographic printing flexible rubber plate and a manufacturing method thereof, wherein the nitrile rubber comprises polyacrylamide, the prepared nitrile rubber color surface rubber, bonding layer and framework material are cotton cloth, and the nitrile rubber color surface rubber, bonding layer rubber and framework material of the flexible rubber plate are adopted.

CN104908472A discloses a formulation for a multilayer photosensitive offset printing plate, which comprises a surface sheet, a protective layer, an adhesive layer, a photosensitive resin layer, a substrate; the main formula of the photosensitive resin layer is as follows: polyvinyl alcohol, the polymerization degree of which is 400-980, hydroxymethyl acrylamide, alpha-hydroxymethyl benzoin methyl ether, hydroquinone and dimethyl sulfoxide.

CN105283319B discloses a plate material for flexographic printing, which comprises: comprisesA printing layer for laser engraving comprising a rubber and an inorganic porous material containing carbon black and having a thickness of 40m per 1g of the rubber²Above and 1000m²The following specific surface area; a compression layer; a base fabric layer disposed between the printing layer for laser engraving and the compression layer; a reinforcing layer; and an adhesive layer made of a rubber substrate disposed between the compression layer and the reinforcing layer and in contact with the reinforcing layer, wherein the flexographic printing plate material has a thickness of more than 2.75mm and 7mm or less, a ratio of the thickness of the printing layer for laser engraving to the thickness of the flexographic printing plate material is 10% or more and 78% or less, and a ratio of the thickness of the compression layer to the thickness of the flexographic printing plate material is 6% or more and 78% or less.

CN103158330B discloses a flexographic printing method for implementation on offset printing presses, wherein a coating fluid is transferred from an anilox roller directly onto the rubber-elastic circumferential surface of a transfer cylinder; directly transferred by the rubber-elastic circumferential surface onto the non-rubber-elastic circumferential surface of the first drum; directly transferred by the non-rubber elastic circumferential surface to the flexographic plate on the second cylinder; directly transferring the flexographic printing plate to a printing stock.

CN204431910U discloses a composite printing plate roller, which is a hollow cylinder and comprises a supporting inner layer, an elastic layer, a supporting outer layer, a filling inner layer and a filling outer layer which are sequentially arranged from inside to outside, wherein the supporting inner layer is made of glass fiber and is in contact with a mandrel; the elastic layer is made of elastic materials; the outer support layer is made of glass fiber; the inner filling layer is filled with polyurethane material; the outer filling layer is in contact with the printing material, and the outer filling layer is made of polyurethane.

JP2013/066253a discloses a plate for flexographic printing comprising: printing layer for laser engraving comprising a rubber and an inorganic porous material, wherein the inorganic porous material is carbon black and the inorganic porous material has a thickness of 90m per 1g of the rubber²A specific surface area of 700m2 or more; a compression layer; a base fabric layer disposed between the printing layer for laser engraving and the compression layer; reinforcing layer(ii) a And an adhesive layer made of a rubber substrate and disposed between the compression layer and the reinforcing layer and in contact with the reinforcing layer.

JP2977014A discloses a method of manufacturing an offset printing blanket comprising: (a) adopting a surface rubber layer as a printing surface layer on at least one layer of base material; (b) directly bonding vulcanized fiber paper on the surface rubber layer; (c) vulcanizing vulcanized steel paper by heating; (d) removing the vulcanized paper; and (e) grinding the surface of the face rubber layer, wherein the vulcanized fiber paper has a surface pH of at least 6.0.

US20030186029a1 discloses a printing compressive blanket comprising two fabric layers and an adhesive layer, a surface rubber layer, and a compressive layer disposed between the fabric layers and the surface rubber layer, the compressive layer containing spherical voids and other shaped voids formed by microspheres.

WO1993018913a1 discloses an offset printing blanket whose compressed layer is prepared by (a) uniformly dispersing highly molten thermoplastic microspheres a in elastomer B to form high melting microspheres; (b) coating microspheres containing an elastomer on the bottom fabric layer; (c) vulcanizing the coated bottom fabric layer at 80-150 ℃ for 1-6 hours to form a compressed layer with uniform compressibility, bonding the layers, and finally vulcanizing and curing the layers to form the layered printing blanket.

"correct use of air cushion rubber cloth and impaired restoration thereof", yellow clock, printing technique, 2012 4 th year, point out that the rubber cloth that adopts in the offset printing mainly has two kinds of ordinary rubber cloth and air cushion rubber cloth, and ordinary rubber cloth generally is cohered through the sizing material by rubber layer and base cloth layer and forms, and the air cushion rubber cloth has increased the one deck air cushion again on this basis, and the air cushion layer of air cushion rubber cloth comprises very little gasbag body, at the printing in-process, because the existence of these gasbag bodies, can reduce the deflection of rubber cloth.

However, the plate making method of the resin plate is time-consuming and labor-consuming, and the other serious defect is that the waste liquid after the plate washing affects the human health, namely the environmental protection of the production environment. Meanwhile, the screen dots of the flexible printing photosensitive resin plate are less than 5%, so that the screen dots are easily enlarged in the printing process, and the printing precision is influenced.

Therefore, there is a need in the art for a cost-effective, high-printing-precision, and environmentally friendly printing plate that can replace resin plates.

Disclosure of Invention

In order to solve the technical problems, the inventor of the invention designs a rubber plate material capable of being directly engraved and formed by laser through further deep research and a large amount of experiments on the basis of previous large amount of research and through cooperative research and development and innovative change of the prior art, and the rubber plate material can change the manufacturing mode of a flexible resin plate, cannot generate industrial hazardous waste in the process of making a rubber flexible engraving plate, and simultaneously improves the reproduction performance of mesh points below 5% in the printing process.

In one aspect of the present invention, there is provided a rubber flexographic plate, wherein the rubber flexographic plate has a three-layer structure comprising an engraving layer (also referred to as a cover stock), an adhesive layer (also referred to as an adhesive layer), and a backing layer, wherein the engraving layer, the adhesive layer, and the backing layer are arranged in this order from top to bottom.

Preferably, the engraved layer described above is used as a surface layer gum for a rubber flexo-engraved plate.

Preferably, the engraving layer is a rubber layer.

Preferably, the rubber of the rubber layer is prepared by a mixing method. More preferably, the rubber of said rubber layer contains inorganic mineral particles.

Further preferably, the inorganic mineral particles are nanoparticles.

In a particularly preferred embodiment, the rubber of the rubber layer is a nanoparticle inorganic mineral particle modified (i.e., compounding modified) rubber, preferably the nanoparticle inorganic mineral particles are nano bentonite particles.

In the inorganic mineral particle-modified rubber, the rubber is 100 parts by weight, and the bentonite is 1 to 10 parts by weight, preferably 3 to 8 parts by weight.

More preferably, the rubber further contains 3-10 parts by weight of SiO₂And (3) nanoparticles.

Preferably, the bentonite nanoparticles have an average diameter of 20-100nm, preferably 40-90 nm.

Preferably, the SiO₂The nanoparticles have an average diameter of 40 to 180nm, preferably 50 to 150 nm.

The rubber layer is preferably produced by a method comprising the steps of:

(1) mixing natural rubber with nanometer bentonite particles and SiO₂Nanoparticles, sulfur (i.e., elemental sulfur or a compound capable of providing elemental sulfur as sulfur), and a vulcanization accelerator represented by the following formula (I):

formula (I)

Wherein, the natural rubber is 100 weight portions, the nano bentonite particles are 1 to 10 weight portions, and SiO is₂3-10 parts of nano particles, 1-5 parts of sulfur and 1-3 parts of vulcanization accelerator shown in formula (I); mixing the mixture at 50-65 ℃ for 5-30 minutes at a mixing speed of 50-200rpm to prepare a blend;

(2) the mixture was pressed into a slab using a press and then maintained at a temperature of 145-155 ℃ for 30-60 minutes, thereby obtaining a rubber layer.

The thickness of the rubber layer can be selected according to the actual printing process, as will be appreciated by those skilled in the art.

In the method, the use of the nano bentonite particles can increase the capacity of the rubber layer for absorbing the non-polar solvent by 5-10%. In addition, the vulcanization accelerator is used to effectively reduce the vulcanization time, and preferably to avoid the deterioration of rubber properties due to too long vulcanization time.

It has also been found that SiO₂The use of nanoparticles can significantly improve tensile strength and fracture deformation, especially when nano-bentonite particles and SiO₂When the nanoparticles are used together, 1 part by weight of SiO is added₂Nanoparticles, capable of reducing the use of about 3-4 parts by weight of nano-bentonite particles and capable of obtaining almost the same tensile strength and fracture deformation.

In an alternative or preferred method, said step (2) may be replaced by the following steps: heating is carried out by respectively contacting two surfaces of the slab by using two heating rollers, the two rollers apply pressure to the slab while heating, the surface temperatures of the two heating rollers are respectively 140-160, and the heating time is 20-60 minutes, wherein the temperature difference of the two heating rollers is 5-10 ℃, thereby preparing the rubber layer.

Preferably, the two compression rollers apply the extrusion pressure on the plate blank to be 5.0-20.0N/cm²。

Research shows that when the temperature of the two heating rollers is 5-10 ℃ different from that of heat preservation heating or isothermal heating of the two surfaces, a temperature gradient difference can be formed on the two surfaces, the temperature gradient difference is favorable for forming ordered directional arrangement of internal textures of vulcanized rubber, the collapse of a rubber layer can be effectively prevented, the thickness unevenness can be reduced, and formed cells are more ordered and uniform, so that the service life and the printing precision are higher.

In a particularly preferred embodiment, the bentonite is preferably a modified bentonite. The nano bentonite particles are preferably modified nano bentonite particles.

Preferably, the nano-bentonite is modified by the following method: (1) suspending bentonite powder in deionized water (preferably, the solid-liquid weight ratio is 1:3-1: 5), and performing ultrasonic dispersion treatment; (2) adding dodecanedioic acid, lauric acid and mercaptobenzothiazole into the bentonite powder, wherein the dosages of the dodecanedioic acid, the lauric acid and the mercaptobenzothiazole are respectively 1-5wt.%, 1-5wt.% and 0.5-3.0wt.% of the bentonite powder, and continuing the ultrasonic dispersion treatment; (3) filtering and drying to obtain the modified nano bentonite particles.

The bentonite nanoparticles can be kept stable by deionized water dispersion. Reversible aggregation of nanoparticles with diameters above 80nm was detected after 30-35 days.

When dodecanedioic acid and lauric acid are added after the initial dispersion, the surface of the bentonite particles can be made to have certain lipophilicity (namely hydrophobicity) so as to be beneficial to the dispersion of the bentonite particles, and the free carboxyl groups shown can generate a grafting effect during curing, can induce polar interaction with other carboxyl groups or epoxide sites, can be beneficial to the reduction of mobility and the formation of crosslinking, and the polar interaction can significantly influence the physical properties of the elastomer, for example, the tensile property of the rubber forming elastomer is improved by the grafting crosslinking.

In addition, the lipophilicity can enable the mercaptobenzothiazole to be firmly adsorbed on the surface of the bentonite particles, and during vulcanization, the bentonite particles and the rubber matrix have particularly good compatibility through the dual functions of crosslinking and vulcanization of the mercaptobenzothiazole in the rubber matrix, so that the generation of segregation can be effectively avoided. This crosslinking also improves the tensile properties of the shaped elastomers.

In a preferred embodiment of the invention, the adhesive layer is made of a rubber-based adhesive, so that it has good adhesive properties to both the engraving layer and the backing layer.

Particularly preferably, the adhesive is prepared by the following method: mechanically masticating epoxidized natural rubber on a two-roll mill for 5-10 minutes, then cutting the masticated rubber sheet into strips and dissolving in 50mL of toluene (rubber to toluene ratio of 1:1-1:4 g/mL), in a closed container at 25-30 ℃ for 12-30 hours in a conditioning chamber to ensure complete dissolution; then adding the crushed coumarone-indene resin under stirring, wherein the weight ratio of the coumarone-indene resin to the epoxidized natural rubber is 1:8-1:16, uniformly stirring, preferably stirring for 3-6 hours at 30-60 ℃ to obtain the adhesive.

The adhesive is a rubber-based adhesive, has good adhesive property to both a carving layer and a backing layer, and has the peel strength of 400-600N/m under the thickness of 90-200 mu m. The adhesives made by the process of the invention consistently exhibit higher peel strength, greater flexibility and strain-induced crystallization than epoxidized natural rubber adhesives. And it has also been found that increasing the coating thickness will increase the peel strength of the adhesive. It has also been surprisingly found that the adhesive has a pressure sensitive effect and a particularly good adhesion during the press-on manufacturing of the flexographic engraving plate.

In a preferred embodiment of the invention, the backing layer is a fibrous backing layer. More preferably, the fibrous backing layer is a flat woven fibrous fabric.

Preferably, the thickness of the fiber supporting layer is 0.20-0.60mm, the tensile strength is more than or equal to 70kgf/cm, and the elongation at break is less than or equal to 5.5%.

In another aspect of the invention, there is provided a method of making a rubber flexographic engraving as described above, the method comprising: and applying an adhesive layer on the backing layer, then applying an engraving layer on the adhesive layer, and then performing pressing and vulcanization to obtain the rubber flexible printing engraving plate.

Preferably, the application is performed by coating or pressing.

The vulcanization can be carried out by a drum vulcanizer.

And (4) after vulcanization, polishing treatment is preferably carried out to prepare the final rubber flexible printing engraving plate.

The rubber flexible printing engraving plate has obvious advantages and effects, overcomes the defects of the prior art, changes the plate making mode of the printing plate used in the prior domestic flexible printing, removes the traditional step of washing the plate by solvent, meets the requirement of environmental protection, reduces the plate making cost, improves the structure and the manufacturing process of the flexible printing plate, improves the reproducibility and the printing press resistance of the printing plate and improves the economic benefit of enterprises.

Drawings

FIG. 1 is a schematic structural view of a rubber flexible engraving plate according to the present invention, wherein 1 denotes an engraving layer, 2 denotes an adhesive layer, and 3 denotes a backing layer;

FIG. 2 is an AFM image showing modified bentonite nanoparticles according to the invention, wherein the size range is 20-90nm, 3D 5 x 5 μm;

fig. 3 is an SEM micrograph of a cracked surface of a rubber layer (according to example 1) made according to the present invention using modified bentonite particles, when tested.

Fig. 4 is an SEM micrograph of a cracked surface of a rubber layer made using unmodified bentonite particles when tested.

Detailed Description

The following are specific examples and comparative examples illustrating the present invention, but the present invention is not limited thereto.

Example 1

Suspending 100g of bentonite powder (purchased from Tianjin Yandong mineral products company) in 400 deionized water, performing ultrasonic dispersion treatment for 30 minutes at a frequency of 18.5kHz, an effective power of 90W/L and an ultrasonic vibration amplitude of 3μm, then adding dodecanedioic acid, lauric acid and mercaptobenzothiazole into the bentonite powder, wherein the dosages of the dodecanedioic acid, the lauric acid and the mercaptobenzothiazole are respectively 2wt.%, 2wt.% and 1.5wt.% of the bentonite powder, continuing performing ultrasonic dispersion treatment for 20 minutes, filtering and drying to obtain modified nano-bentonite particles; then natural rubber (purchased from Hainan sea rubber company) and the modified nano bentonite particles and SiO₂Mixing nanoparticles, sulfur and a vulcanization accelerator represented by the formula (I) in the specification, wherein the natural rubber accounts for 100 parts by weight, the nano bentonite particles account for 9 parts by weight, and SiO₂5 parts by weight of nanoparticles, 2 parts by weight of sulfur and 1 part by weight of a vulcanization accelerator represented by the formula (I); the mixture was mixed at 60 ℃ for 20 minutes at a mixing speed of 150rpm to prepare a blend, after which the mixture was pressed into a slab after 300 μm using a press, and then maintained at a temperature of 150 ℃ for 40 minutes, thereby preparing a rubber layer.

The rubber layer was tested for peel strength, tensile strength and elongation at break, with a peel strength of 720N/m, a tensile strength of 12.8Mp and an elongation at break of 680%, with the peel strength being tested in accordance with ASTM D907 and the tensile strength and elongation at break being tested in accordance with the corresponding GB standard.

Comparative example 1

Example 1 was repeated with the only difference that the bentonite was a nano-bentonite which had not been modified with dodecanedioic acid, lauric acid and mercaptobenzothiazole. The rubber layer peel strength was 516N/m, the tensile strength was 7.6Mp and the elongation at break was 410% as measured.

The performance indexes, particularly tensile strength, were significantly decreased compared to example 1, presumably due to the fact that the unmodified nano-bentonite particles are less compatible with rubber and no crosslinking is generated in the rubber.

Comparative example 2

Example 1 was repeated with the only difference that no SiO was added₂Nanoparticles, but SiO₂The nano-particles are replaced by modified nano-bentonite particles with equal dosage. The rubber layer peel strength was tested to be 610N/m, the tensile strength was 10.4Mp and the elongation at break was 510%.

Compared with the example 1, only a single nanometer bentonite particle is used in the rubber mixing, and all index performances are reduced to a certain extent. This result seems to be somewhat unexpected. XRD examination found that for rubber mixtures without added silica an increase in the interlayer distance was observed, from about 1.45nm to 2.45nm, which demonstrates that the presence of silica almost completely eliminates the effect of the organic modification of bentonite on the interlayer distance for rubber mixtures and that silica has a favorable marginal effect on tensile strength and elongation at break.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred to herein are incorporated herein by reference to the extent that no inconsistency is made.

Claims

1. The rubber flexible printing engraving plate is characterized by being of a three-layer structure and comprising an engraving layer, an adhesive layer and a lining layer, wherein the engraving layer, the adhesive layer and the lining layer are sequentially arranged from top to bottom, the engraving layer is a rubber layer, rubber of the rubber layer is nano inorganic mineral particle modified rubber, namely mixing modified rubber, the nano inorganic mineral particles are nano bentonite particles, and in the nano inorganic mineral particle modified rubber, rubber is100 parts of rubber, 1-10 parts of bentonite, and 3-10 parts of SiO₂Nanoparticles, the average diameter of the nano bentonite particles being 20-100 nm;

the rubber layer is prepared by a method comprising the following steps:

(1) mixing natural rubber with nanometer bentonite particles and SiO₂Nanoparticles, sulfur, i.e. elemental sulfur or a compound capable of providing elemental sulfur in terms of sulfur, and a vulcanization accelerator represented by the following formula (I):

formula (I)

Wherein, the natural rubber is 100 weight portions, the nano bentonite particles are 1 to 10 weight portions, and SiO is₂3-10 parts of nano particles, 1-5 parts of sulfur and 1-3 parts of vulcanization accelerator shown in formula (I); mixing the above-mentioned mixture at 50-65 ℃ for 5-30 minutes at a mixing speed of 50-200rpm to prepare a blend;

(2) the blend was pressed into a slab using a press and then maintained at a temperature of 145-155 ℃ for 30-60 minutes to prepare a rubber layer.

2. A rubber flexographic engraving plate according to claim 1, characterized in that said engraving layer is used as a surface layer glue for the rubber flexographic engraving plate.

3. A rubber flexographic engraving plate according to claim 1 or 2, characterized in that said backing layer is a fibrous backing layer.

4. The rubber flexographic engraving plate of claim 3, wherein the fiber backing layer has a thickness of 0.20 to 0.60mm, a tensile strength of 70kgf/cm or more and an elongation at break of 5.5% or less.

5. A method of making a rubber flexographic engraving according to any of the preceding claims, characterized in that it comprises: and applying an adhesive layer on the backing layer, then applying an engraving layer on the adhesive layer, and then performing pressing and vulcanization to obtain the rubber flexible printing engraving plate.

6. The method of claim 5, said applying being by coating or pressing.