JP4562134B2 - Pen core and processing method thereof - Google Patents

Description

  The present invention relates to a pen core for a writing instrument that is interposed between an ink tank and a pen tip and temporarily retains ink in response to a pressure change, and further relates to a pen core processing method for modifying the surface of the pen core. It is.

Conventionally, in order to supply the ink filled in the ink tank to the pen tip, as a member for a writing instrument that is interposed between the ink tank and the pen tip and temporarily stores the ink according to the pressure change, Various pen cores made of comb-shaped synthetic resin are used.
When the internal pressure of the ink tank increases and the ink is about to leak out from the pen tip, the pen core temporarily guides the ink to the ink reservoir such as the comb groove of the pen core, and the internal pressure of the ink tank When the ink is lowered and the ink is about to retreat, the ink stored in the ink reservoir is retreated to the ink tank instead of the retreat, and the ink supply is stabilized. The pen core has a variety of shapes such as a comb groove shape and a bellows shape.

  In order to achieve a stable supply function of ink, there are things that have been devised and solved the shape, but because it is a shape solution, it is difficult to continue using the conventional pen core as it is, Since the performance of each product varies, it is difficult to use it for general purposes.

On the other hand, there are some that solve the problem by making the material of the pen core specific or chemically modifying the surface. From the standpoint of achieving a stable ink supply function, the pen core must be wetted to some extent when supplying ink. But don't get too wet. This is because it becomes difficult to retain the ink.
For this reason, a modification method has been conventionally used in which the pen core is immersed in an etching solution containing sulfuric acid as the main ingredient and then washed with water to oxidize and roughen the pen core surface to increase the surface tension of the pen core surface. I came.
However, since the etching solution used in the above method uses a mixed solution composed of chromic anhydride and phosphoric acid with sulfuric acid as the main ingredient, it is toxic and may irritate the skin and mucous membranes and sometimes cause burns. There was a problem that it was difficult to handle.

  Further, as the surface modification, the above-described etching treatment alone is not sufficient, and the desired ink supply performance was obtained through subsequent thin film formation with a synthetic resin, etc., so that the work was complicated and costly. It was.

  Further, Patent Document 1 and the like also propose a synthetic resin ink guide member provided with a surface layer made of an inorganic material and surface-modified. However, the work process is still complicated, and there is a problem in the fixing property of the layer due to the compatibility between the inorganic material and the synthetic resin.

On the other hand, Patent Documents 2 to 3 have been proposed as various hydrophilic coatings on the surface of a synthetic resin pen core material.
Patent Document 2 discloses, as specific examples, hydrophilic groups such as —OH, ═CO, —COOH, —NH ₃ , —SO ₃ H, and the like, and resins having them.
Patent Document 3 discloses polyvinyl alcohol and acrylic acid esters as main ingredients of hydrophilic solutions.
In this document, etc., there is a description that the wettability of the ink is modified by the surface modification effect by those resins, but in Patent Document 2, depending on the exemplified hydrophilic coat, The modification effect of the pen core is insufficient, and in Patent Document 3, since the modified film is a swollen film, it may be dissolved into the ink over time, which is problematic. It was.

In Patent Document 4, as a method for modifying the surface of a styrene resin, a polyacrylate emulsion treatment, a sulfuric acid treatment (first time), a polyvinyl acetate emulsion treatment, and a sulfuric acid treatment (second time) are carried out in this order. What has been proposed. The thing of patent document 4 is characterized by the process of forming different materials in order. Specifically, after forming a polyacrylic acid ester film that is easy to adhere to a styrene resin material, the polyacrylic resin is formed. The surface of the acid ester film is roughened by the first sulfuric acid treatment, and then the surface condition is adjusted by another polyvinyl acetate emulsion treatment, which is another emulsion, followed by a second sulfuric acid treatment.
However, because of the sulfuric acid treatment, there are still problems such as safety, etc., and it is necessary to perform several treatments with an emulsion of another chemical species. The complexity could not be solved. In addition, since there is only a vinyl acetate film to be formed in the final process on the surface, the surface modification property is insufficient.

Furthermore, Patent Document 5 proposes an example using low-temperature plasma treatment, but the apparatus becomes large.
JP-A-6-92081 Japanese Utility Model Publication No. 60-178174 JP-A-9-315079 JP-A-3-32896 Japanese Patent No. 2886381

  The present invention proposes a pen core with an appropriate surface modification and a method for treating the pen core of a writing instrument that is interposed between an ink tank and a nib and temporarily retains ink in response to a pressure change. Therefore, the present invention proposes a well-balanced solution for achieving the above-described problems, in particular, the simplification of the surface modification process and the surface modification performance.

In order to solve the above problems, the present invention has completed the pen core of the present invention and the treatment method thereof by, for example, coating the surface of the pen core with a copolymer containing vinyl acetate and an acrylate ester.
That is, the present invention
“1. A pen core of a writing instrument that is interposed between an ink tank and a nib and temporarily retains ink in response to a change in pressure, and the surface thereof is covered with a copolymer containing vinyl acetate and an acrylate ester. A pen core characterized by that.
2. The pen core according to item 1, wherein the ester group constituting the acrylic acid ester of the copolymer has 5 or less carbon atoms.
3. A pen core according to claim 1, wherein the pen core is coated with an emulsion of the copolymer.
4). The pen core according to any one of Items 1 to 3, wherein a static contact angle of the coated pen core with respect to water is 60 to 80 °.
5). The pen core according to any one of Items 1 to 4, wherein the acrylic ester content in the copolymer is 3 to 30% by mass.
6). The surface covering of the pen core of the writing instrument that is interposed between the ink tank and the pen tip and temporarily retains the ink in response to a pressure change is the one described in any one of the first to fifth items. A method of treating a pen lead that modifies the surface of the pen lead. ".

  According to the pen core and the processing method therefor, the process film is a uniform thin film, and the ink wettability is good while the process is simplified without passing through a dangerous process such as a black mixed process. It has excellent ink holding power even when the tank is subjected to pressure changes, no ink drooping or swallowing, etc. is there.

As described above, the main part of the present invention is that the surface of the pen core is coated with a copolymer containing vinyl acetate and an acrylate ester.
By covering the surface of the pen core with the above copolymer, a pen core having good adhesion to the base resin material and having appropriate hydrophilicity can be obtained.

As the base resin material, AS resin, ABS resin, PP resin, PE resin, nylon, and various other synthetic resins can be used, but AS resin is preferable for reasons of dimensional accuracy and the like.
However, a synthetic resin material such as an AS resin has a large surface hydrophobicity as it is, and is inferior in ink wettability. Therefore, it is necessary to modify the surface.

The copolymer used in the present invention is a copolymer containing at least vinyl acetate and an acrylate ester in a copolymer unit as a main skeleton, and also includes three or more multi-component copolymers.
Whereas conventional surface-modified polymers that are not composite copolymers need to be processed in several orders, the above-mentioned copolymer contains vinyl acetate and acrylate ester in a complex manner, so synergy between the two can be expected. As a result, the adhesion of the pen core to the base resin material and the control of the wettability with respect to the ink are solved once.
In other words, since the copolymer contains hydrophobic vinyl acetate and has high adhesion to the base resin material, and also contains a hydrophilic acrylic acid ester, water, that is, water-based ink is used. Good wettability can be exhibited.

  The static contact angle of the pen core coated with the copolymer with water is preferably 60 to 80 °. In order to function satisfactorily as a pen lead, it is not necessary to just get wet with water, but it is necessary to adjust it to an appropriate range. If it is within the above range, good performance can be obtained in the water-based ink, and a suitable static contact angle with the water-based ink is 40 to 75 °. Originally, the contact angle with the ink to be used is the most suitable element for showing the performance of the pen core, but it is difficult to unconditionally specify the processing process due to variations in the composition present in the ink. In the present invention, it has an important meaning where it is defined by replacing it with water.

  If the static contact angle of the pen core with respect to water is smaller than this range, that is, too wet, the ink tends to come out too much, and the comb groove fills the ink in the comb groove structure and the surrounding environment. Depending on the state of change (under reduced pressure), the ink may hang down, which is not preferable. On the other hand, if the static contact angle is larger than this range, that is, if it does not get wet, there is a strong tendency that ink is not supplied to the pen core, so the ink followability is poor, and the performance as a writing instrument cannot be satisfied in the first place. Yes, not preferred.

As described above, the copolymer used in the present invention is a copolymer containing at least vinyl acetate and an acrylate ester in the main copolymer unit, and each copolymer unit contains a derivative thereof. Species can be used.
In addition, it includes three or more multi-component copolymers, and a suitable example is a multi-component copolymer of vinyl acetate-alkyl acrylate ester, and a good use of vinyl acetate-alkyl acrylate-crotonate copolymer. it can.

The vinyl acetate-alkyl acrylate ester-crotonic acid copolymer is a ternary copolymer of vinyl acetate, alkyl ester of acrylic acid and crotonic acid.
When using not only the copolymer but also a multi-component copolymer, it is necessary that the molecular weight and the carbon chain length of the chemical species to be composed together with the acrylate ester in the copolymer are not excessive. If the amount is too large, the static contact angle may not be improved even if the copolymer unit as the main part of the copolymer is suitable.

  Further, if the ester group constituting the acrylate ester in the copolymer used in the present invention is excessive, there is a tendency to cause the same problem as described above. Specifically, the number of carbon atoms in the ester group constituting the acrylate ester in the copolymer is preferably 5 or less.

  Furthermore, when the copolymerization unit constituting the copolymer used in the present invention includes derivatives each having a branched chain or a functional group, it is necessary that the molecular weight of the side chain or the like is not excessive. The problem when it is excessive is the same as the reason that the molecular weight and carbon chain length of the chemical species of the copolymer unit itself are not excessive.

The acrylic ester content in the copolymer used in the present invention is preferably 3 to 30% by mass.
This is because the acrylic ester content directly affects the degree of hydrophilicity of the modified coating. If it is below the above range, the tendency of hydrophobicity is too strong and the wettability is lost. As a result, the ink dischargeability tends to deteriorate. When the above range is exceeded, the balance is lost due to excessive hydrophilicity, and as a result of being too wet, there is a tendency that undesired symptoms are likely to occur at the time of writing, such as ink dropping or dripping or ink being excessively discharged.

When the copolymer treatment is performed on the pen core, it is preferable that the copolymer is provided with an emulsion of the copolymer because a uniform thin film with better adhesion can be obtained.
About the processing method by an emulsion, the target performance can be acquired by diluting the emulsion of the said copolymer suitably, and apply | coating to a pen core. There is no particular limitation on the application method at that time, but for example, it can be easily obtained by simply immersing the pen core material in the emulsion, then draining it and drying it.
Further, in order to further improve the wettability and the adhesion, a pretreatment by a conventional method such as roughening the surface of the pen core material in advance may be performed.

  As the ink used for the writing instrument incorporating the pen core of the present invention, water-based ink in which a coloring material such as a dye or pigment is dissolved and dispersed based on water can be used. Additives such as surfactants, viscosity modifiers, pH adjusters, and preservatives can be appropriately used in the ink. Further, the ink preferably has a surface tension of 35 to 45 mN / m, a specific gravity of 1.0 to 1.2, and a viscosity of about 1.1 to 1.3 mPa · s.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1
A comb-groove pen core made of AS resin as a base material was prepared as a molded member, the pen core was immersed in an aqueous solution containing a commercially available alkaline detergent, and then washed and dried (pretreatment 1). Thereafter, the pen core was blasted to roughen the surface.
Next, the pen core was immersed for 5 minutes in an emulsion (emulsion concentration 1 mass%) of a vinyl acetate-acrylic acid alkyl ester-crotonic acid copolymer (acrylic ester content 3 mass%) as a copolymer used in the present invention. After removing the excess liquid and forming a uniform thin film, the film was dried at 50 ° C. for 12 hours to obtain a pen core having a thin film of vinyl acetate-acrylic acid alkyl ester-crotonic acid copolymer on the surface. It was.
The static contact angle with respect to the water of the thin film of the vinyl acetate-acrylic acid alkyl ester-crotonic acid copolymer used in Example 1 was 67.5 °.

The measurement method of the static contact angle with respect to water was measured as follows.
Static contact angle (Measurement method: Droplet method)
Molded with the same material as the pen core material, water droplets are formed on the plate on which the copolymer thin film is formed as described above, and three points on the water droplets are specified, and the angle between the air / liquid interface and the plate surface is measured. By doing so, the contact angle was obtained. The measurement was repeated 5 times, and the average value was taken as the contact angle in the present invention.

Writing test The obtained pen core was incorporated in a writing instrument, and the writing test was done.
As a writing instrument, a fountain pen FKK1000R manufactured by Pilot Corporation was used.
As the ink, a black fountain pen black ink and a blue ink manufactured by Pilot Corporation were used, and the ink physical properties were as follows.
Black ink: surface tension 39 mN / m, specific gravity 1.0, viscosity 1.3 mPa · s
Blue ink: surface tension 44 mN / m, specific gravity 1.0, viscosity 1.1 mPa · s

Each specific evaluation was performed as follows.
-Drooping performance The presence or absence of a drop from the pen tip when the surrounding area was placed under reduced pressure was observed.
○: Drop formation and drop dropping were not observed.
Δ: Drop formation was observed, but no drop was observed.
X: Dropping was observed.
-Writing performance The ink following ability was observed when writing straight on the filter paper.
○: A continuous handwriting was obtained.
Δ: Some lines were cut off.
X: Ink follow-up failure occurred and could not be written.

Examples 2-6
A pen core having a thin film of the copolymer formed on the surface was obtained in the same manner as in Example 1 except that the copolymer used in Example 1 was changed to that shown in Table 1.
Each acrylate content, ester group carbon number, contact angle with water, evaluation, etc. are shown in Table 1.

Comparative Examples 1-3
A pen core having a thin film of the polymer formed on the surface thereof was obtained in the same manner as in Example 1 except that the copolymer used in Example 1 was replaced with the resin material described in Table 1.
Table 1 shows the contact angle and evaluation of each water.

From Example 1 and Examples 4 to 6, it is necessary as an optimal pen core treatment material that the molecular weight, carbon chain length, and carbon number of the ester group of the chemical species composing the acrylate ester in the copolymer are not excessive. I understand that.
If it is excessive as in Examples 2-3 (ester group = ethylhexyl), the static contact angle may not be in the optimum range even if the acrylate content is appropriate.

  Further, by comparing the examples and comparative examples, even when the contact angle is close to the preferred range, when a chemical species that is not a copolymer containing vinyl acetate and acrylate is used as the resin for surface modification, It is inferior to sagging performance, and in terms of writing performance, when writing on plain paper, etc., even if it can be written to some extent, it is required to have high ink followability in filter paper with high ink permeability as in the above writing test. In such use, the performance was not sufficient, and a suitable pen core could not be obtained.

The pen core of the present invention and the pen core obtained by the treatment method of the present invention are suitable for a pen core of a writing instrument that is interposed between an ink tank and a pen tip and temporarily retains ink according to a pressure change. Available.

Claims (6)

  A pen core of a writing instrument that is interposed between an ink tank and a nib and temporarily retains ink in response to a change in pressure, and whose surface is coated with a copolymer containing vinyl acetate and an acrylate ester. Characteristic pen core.   The pen core according to claim 1, wherein the ester group constituting the acrylic acid ester of the copolymer has 5 or less carbon atoms.   3. A pen core according to claim 1, wherein the pen core is coated with an emulsion of the copolymer.   The pen core according to claim 1, wherein the coated pen core has a static contact angle with water of 60 to 80 °.   The pen core according to any one of claims 1 to 4, wherein an acrylic ester content in the copolymer is 3 to 30% by mass. 6. A pen core, wherein the pen core of the writing instrument is interposed between the ink tank and the nib and temporarily retains ink in response to a change in pressure. A pen core treatment method for modifying the surface of the surface.