JP2006305885A - Writing utensil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a writing utensil, with a properly modified surface to an ink applied, which is equipped with an ink felt and an ink, with such advantages that a processed film is uniformly thin although it undergoes a simplified process without passing through a dangerous process such as a chromate intermixing treatment, the wetting properties to the ink are satisfactory, the ink retaining force is excellent even in case an ink tank receives a pressure change, no ink dripping and abnormal intake occur, the writing follow-up properties of the ink are good, and especially a well-balanced remedy for solving inherent problems from the viewpoint of compatibility of the simplification of a pen felt surface modification process with a surface modification performance, can be proposed. <P>SOLUTION: This writing utensil has at least, the pen felt, ink tank and ink to be packed in the ink tank. In addition, the writing utensil uses the pen felt with its surface modified in a special way so that a specific contact angle with the ink to be used can be formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to a writing instrument having at least a pen core, an ink tank, and ink filled therein, and to a writing instrument using a pen core with a special surface modification so as to have a specific contact angle with respect to the ink used. It is.

Conventionally, writing instruments directly packed with ink have been interposed between the ink tank and the nib to supply the ink filled in the ink tank to the nib, and the ink is temporarily applied according to the pressure change. Various pen cores made of a comb-shaped synthetic resin or the like are used as members for writing instruments to be retained.
When the internal pressure of the ink tank increases and the ink is about to leak 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 ink supply function, the pen core shape has been devised to solve the problem, but since it is a geometric solution, it is difficult to continue using the conventional pen core as it is. Because the performance of each type varies, it is difficult to use 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, conventionally, the pen core is immersed in an etching solution containing sulfuric acid as the main ingredient and then washed with water to oxidize the pen core surface and roughen it 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 etching treatment alone is not sufficient, and the desired ink supply performance has been obtained through subsequent thin film formation with a synthetic resin, etc., so that the work is 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 relates to a writing instrument having at least a pen core, an ink tank, and ink filled therein, and a writing instrument using a pen core with a special surface modification so as to have a specific contact angle with respect to the ink used. The present invention proposes a well-balanced means for solving the above-described problems, particularly the simplification of the surface modification process of the pen core and the surface modification performance.

In order to solve the above-mentioned problems, the present invention covers the surface of the pen core with a copolymer containing vinyl acetate and an acrylic ester, and the contact angle with respect to the ink to be used is in a specific range. Completed the pen nib and its treatment method.
That is, the present invention
"1. A writing instrument having at least a pen core, an ink tank, and ink filled therein, the pen core having a surface coated with a copolymer containing vinyl acetate and an acrylate ester, and the coated pen The writing instrument, wherein the contact angle of the lead to the ink is a static contact angle of 40 to 75 ° and a dynamic contact angle of 40 to 70 °, respectively.

  According to the pen core and its processing method in the above writing instrument, the processed film is a uniform thin film without passing through dangerous processes such as black mixed processing, and the wettability of ink is good. In addition, the ink tank has excellent ink holding power even when the pressure changes, there is no ink dripping or swallowing, etc., and there is an excellent effect of obtaining a writing instrument with good ink writing followability. .

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, and the contact angle with respect to the ink to be used is in a specific range.
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 resin material used as the base of the pen core, AS resin, ABS resin, PP resin, PE resin, nylon, and other various 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 above copolymer contains hydrophobic vinyl acetate, it has good adhesion to the base resin material and also contains hydrophilic acrylic acid ester. It is possible to exhibit a good wettability.

  The preferred static contact angle with the aqueous ink used for the pen core coated with the copolymer is 40-75 °. The contact angle with the ink used is the most suitable factor for showing the performance of the pen core.

  If the static contact angle of the pen core with respect to the ink is smaller than this range, that is, if it is too wet, there is a tendency for the ink to come out too much. 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 in the first place tends not to be satisfied. Yes, not preferred.

In the case where it is difficult to generally define the processing process due to variations in the composition present in the ink, a static contact angle with water can be used in combination.
The static contact angle with respect to water is preferably 60 to 80 °. In order to function well as a pen core, it is not necessary to just get wet with water, and it is necessary to adjust to an appropriate range, as in the contact angle with respect to ink. Within the above range, good performance can be obtained in the water-based ink.

  Furthermore, in the present invention, the dynamic contact angle between the ink used and the pen core material needs to be 40 to 70 °. This is because when a writing instrument is actually used, not only the idea of static contact angle but also the idea of dynamic contact angle are required. Regarding the behavior of ink when ink is consumed at the time of writing, for example, the followability of ink, it is considered that the ratio depending on the dynamic contact angle of ink increases.

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 it is too large, the static contact angle and the dynamic 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 of 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 in the case of being excessive is the same as the reason that the molecular weight and the 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, ink drops or drooping tends to occur, or unfavorable symptoms tend to occur at the time of writing such as excessive ink.

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 coloring materials such as dyes and pigments are 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.

  As the writing instrument of the present invention, a desired nib can be selected as the nib. For example, fountain pens, ballpoint pens, felt pens, parallel pens and the like can be mentioned, and they are most useful for writing instruments of the type that write by the capillary force of ink such as fountain pens and parallel pens.

  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 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 for 5 minutes. 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.
After that, a fountain pen nib was attached and an ink cartridge filled with ink was arranged to constitute a writing instrument.
The static contact angle to the ink of the thin film of the vinyl acetate-acrylic acid alkyl ester-crotonic acid copolymer used in Example 1 was 46.7 ° for black ink, 46.7 ° for blue ink, and 44.degree. For the dynamic contact angle for black ink. 2 ° and blue ink 53.5 °.
The static contact angle with water was 67.5 °.

The static contact angle and the dynamic contact angle were measured as follows.
Static contact angle (Measurement method: Droplet method)
Molded with the same material as the pen core material, formed ink (water) droplets on the plate on which the copolymer thin film was formed as described above, specified three points on the water droplets, the air / liquid interface and the plate surface The contact angle was determined by measuring the angle formed. The measurement was repeated 5 times, and the average value was taken as the contact angle in the present invention.

Dynamic contact angle (measuring method: meniscus method)
The ink to be used was stored in a predetermined container, and the height of the meniscus formed when a plate having a length of 50 mm, a width of 10 mm, and a thickness of 2 mm was inserted therein was measured by still image measurement to obtain a contact angle.
For measurement, contact angle meter CA-X type meniscus system option MS-11 type (trade name) manufactured by Kyowa Interface Science Co., Ltd. is used. The contact angle when submerged in the surface) was measured and used as the dynamic contact angle of 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 1
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.
・ Writing performance 2
A filter paper was placed on the pen cut fixed at an angle of 60 degrees, and the ink following ability when moving at a constant speed was observed.
○: Continuous blotting (ink following) was possible.
Δ: There was a part where it was interrupted.
×: Ink follow-up failure occurred and blotting was not possible.

Examples 2-4
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.
Table 1 shows the acrylate content, ester group carbon number, contact angle with ink, contact angle with water, and evaluation.

Comparative Examples 1-5
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 acrylate content, ester group carbon number, contact angle with ink, contact angle with water, and evaluation.

  According to a comparison between the examples and the comparative examples, even when the contact angle is within a preferable range, when a chemical species that does not contain vinyl acetate and acrylate is used as the resin for surface modification, the drooping performance is improved. Inferior, in terms of writing performance, even when writing on plain paper etc., even if it can be written to some extent, use that requires high ink followability in filter paper with high ink permeability as in the above writing test etc. At that time, the performance was insufficient, and a suitable pen core could not be obtained.

  As can be seen from Examples and Comparative Examples 4 to 5, even if the chemical species of the copolymer is appropriate, the required performance of the present invention is not satisfied if the contact angle with respect to the ink is not appropriate. In particular, when the dynamic contact angle is out of the preferred range, there will be a difference in the ink followability in the limit region as in the writing performance 2 test.

Furthermore, from Examples and Comparative Examples 4 to 5, the molecular weight and carbon chain length of the chemical species composing with the acrylate ester in the copolymer, and the carbon number of the ester group being not excessive also affect the optimal pen core treatment material. I understand that.
Even if the acrylate content is appropriate as in Comparative Examples 4 to 5 (ester group = ethylhexyl), the static contact angle may not be in the optimum range. It will not be.

The writing instrument having at least the pen core of the present invention, the ink tank, and the ink filled therein has excellent basic writing performance, and is also excellent in performance of temporarily storing ink in response to pressure change. It can be suitably used as a writing instrument.

Claims (1)

A writing instrument having at least a pen core, an ink tank, and ink filled therein, the pen core having a surface coated with a copolymer containing vinyl acetate and an acrylate ester, and the coated pen core ink A writing instrument, wherein the contact angle with respect to is a static contact angle of 40 to 75 ° and a dynamic contact angle of 40 to 70 °, respectively.