JP2011000712A - Surface treatment method for mold for synthetic resin molding, and mold for synthetic resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for synthetic resin molding with excellent mold releasability.SOLUTION: A surface treatment method for the mold 60 for synthetic resin molding for molding synthetic resin moldings by filling molten synthetic resin in the mold and solidifying the synthetic resin in the mold, includes: a first process S21 forming a polyorganosiloxane membrane containing polyorganosiloxane onto the mold faces 68, 70 of the mold 60 for synthetic resin molding; a second process S22 of hydroxyl group introduction introducing a hydroxyl group to the polyorganosiloxane membrane by cutting part of an organic group exposed on the surface thereof; and a third process S23 of coupling the polyorganosiloxane membrane subjected to the hydroxyl group introduction process, by a coupling agent.

Description

  The present invention relates to a surface treatment method for a synthetic resin molding die and a synthetic resin molding die.

  Synthetic resins are widely used in various fields as industrial materials because of their diverse characteristics and good processability. One method for producing a synthetic resin product is, for example, injection molding. In injection molding, the molding die is filled with molten synthetic resin, and when the filled synthetic resin is solidified, the synthetic resin product is taken out from the molding die. In order to improve the productivity of the synthetic resin product, it is effective to shorten the time for taking out the synthetic resin product from the molding die. Therefore, it is known that a mold release agent such as silicone or fluorine that improves the mold release of the synthetic resin product is applied to the mold surface of the mold using a nozzle (for example, see Patent Document 1).

JP-A-11-226966

  In recent years, synthetic resin products are required to have high precision and high functionality, and molding molds are becoming more complex. When the above-described method of applying the mold release agent to a mold surface having a complicated structure is applied, the mold release agent may not be uniformly applied to the mold surface and the mold release may not be performed smoothly. Therefore, the surface of the product may be scratched when released from the mold, or may be deformed in a remarkable case. For this reason, there is a problem that stable production of synthetic resin products is difficult. Further, the release agent is inferior in adhesion to the mold material, and the release agent adheres to the surface of the synthetic resin product, so that the release agent on the mold surface is peeled off. For this reason, it has been necessary to continue to apply the release agent at a predetermined interval, resulting in problems such as reduced productivity.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  (Application Example 1) A synthetic resin molding die surface treatment method in which a synthetic resin melted in a mold is filled, and the synthetic resin is solidified in the mold to form a synthetic resin molded product. A first step of forming a polyorganosiloxane film containing polyorganosiloxane on the mold surface of the resin mold, and a portion of the organic groups exposed on the surface of the polyorganosiloxane film A second step of performing a hydroxyl group introduction treatment for cutting and introducing a hydroxyl group; and a third step of coupling the polyorganosiloxane film subjected to the hydroxyl group introduction treatment with a coupling agent. A surface treatment method for a synthetic resin molding die.

  According to this method, a film exhibiting characteristics corresponding to the type of coupling agent can be formed on the mold surface of the synthetic resin molding die. Therefore, by employing a coupling agent having releasability as a characteristic, a synthetic resin molding die having a film having excellent releasability on the mold surface can be provided.

  (Application Example 2) The surface treatment method for a synthetic resin molding die as described above, wherein the polyorganosiloxane film is mainly composed of a dialkyl silicone.

  According to this method, in the second step, the bond between the organic group and Si can be cut relatively easily. Therefore, a hydroxyl group can be reliably introduced into this cut portion.

  (Application Example 3) In the first step, the polyorganosiloxane film is formed by a plasma polymerization method.

  According to this method, a polyorganosiloxane film having a uniform and uniform film thickness can be easily formed by performing the plasma polymerization method.

  (Application Example 4) The surface treatment method for a synthetic resin molding die described above, wherein the hydroxyl group introduction treatment in the second step is performed by plasma irradiation.

  According to this method, since the substitution from the organic group to the hydroxyl group proceeds relatively moderately, the introduction amount of the hydroxyl group can be easily adjusted.

  (Application Example 5) The surface treatment method for a synthetic resin molding die described above, wherein the plasma irradiation time in the plasma irradiation is 5 to 10 minutes.

  According to this method, the organic groups present on the surface of the polyorganosiloxane film are replaced with hydroxyl groups at an appropriate ratio. Therefore, the film on the mold surface of the finally obtained synthetic resin molding die has particularly excellent characteristics according to the type of coupling agent. Therefore, by adopting a coupling agent having releasability as a characteristic, a synthetic resin molding die having a film having excellent releasability on the mold surface can be provided.

  (Application Example 6) The surface treatment method for a synthetic resin molding die as described above, wherein the output of the high frequency power in the plasma irradiation is 50 to 500 W.

  According to this method, the organic group present in the polyorganosiloxane film can be reliably replaced with a hydroxyl group.

  (Application Example 7) The surface treatment method for a synthetic resin molding die as described above, wherein the coupling agent is a silane coupling agent.

  According to this method, the monomolecular film composed of the silane coupling agent is formed by combining the hydroxyl group of the polyorganosiloxane film with the reactive functional group of the silane coupling agent relatively easily. Formed on the surface.

  Application Example 8 The surface treatment method for a synthetic resin molding die described above, wherein the coupling agent has a functional group having 10 to 1000 carbon atoms.

  According to this method, by setting the carbon number of the functional group within the above range, the functional groups of the adjacent coupling agents are intertwined in a complicated (three-dimensional) manner, and depending on the type of the coupling agent of the film. The characteristics are improved. Therefore, by adopting a coupling agent having releasability as a characteristic, it is possible to provide a synthetic resin molding die having a film with improved releasability on the mold surface.

  (Application Example 9) In the above synthetic resin molding die, the coupling agent is at least one of those having a liquid repellent functional group and those having a reactive functional group Surface treatment method.

  According to this method, the obtained film has at least one of liquid repellency and reactivity. A film having at least one of liquid repellency and reactivity is excellent in releasability for releasing the synthetic resin product from the mold surface of the synthetic resin molding die. Therefore, a film having excellent releasability can be formed uniformly and uniformly on the entire mold surface of the synthetic resin molding die.

  (Application Example 10) A synthetic resin molding die having a film formed by the surface treatment method for a synthetic resin molding die described above on the mold surface.

  According to this configuration, it is possible to provide a synthetic resin molding die in which a film having excellent releasability is uniformly and uniformly formed on the entire mold surface.

The external appearance perspective view which shows the example of the product manufactured with the synthetic resin shaping | molding die of a present Example. Schematic which shows the structure of the synthetic resin shaping | molding die of a present Example. The flowchart which shows the flow of a synthetic resin molding method. The flowchart which shows the flow of the surface treatment method of a present Example. The longitudinal cross-sectional view explaining the surface treatment method of a present Example. The schematic diagram which shows the film-forming apparatus for enforcing the surface treatment method of a present Example. The schematic diagram explaining the film | membrane formed into a film by the surface treatment method of a present Example.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the vertical and horizontal scales of members or parts may be shown differently from the actual ones for convenience of description and illustration.

(Structure of the type synthetic resin molded)
The synthetic resin molding die of this example will be described with reference to FIGS. FIG. 1 is an external perspective view showing an example of a product manufactured with the synthetic resin molding die of this embodiment, and FIG. 2 is a schematic view showing the structure of the synthetic resin molding die of this embodiment.
As shown in FIG. 1, the product 50 is formed of, for example, a thermoplastic resin such as ABS, PS, PP, etc., and has a rectangular bottom surface, and four rectangular sides from the sides of the bottom surface rise substantially at right angles. It has a box shape.

  The product 50 is manufactured by a synthetic resin molding die (hereinafter referred to as a mold 60) shown in FIG. The mold 60 is generally composed of a first mold 62 and a second mold 64. The first mold 62 and the second mold 64 are joined at a so-called parting surface P. FIG. 2 shows a state in which the first mold 62 and the second mold 64 are combined and the mold 60 is closed. When the mold 60 is closed, a cavity 66 is formed by the first mold 62 and the second mold 64. The shape of the cavity 66 corresponds to the shape of the product 50. That is, the first mold surface 68 of the first mold 62 corresponds to the inner surface 50 a of the product 50 shown in FIG. 1, and the second mold surface 70 of the second mold 64 corresponds to the appearance surface 50 b of the product 50. .

  The first mold 62 is provided with a gate 72 communicating from the outside to the first mold surface 68, a plurality of projecting pins 74 that can reciprocate in the direction of the arrow X in FIG. 2, and a plurality of guide pins 75. Yes. The gate 72 is connected to an injection nozzle (not shown) of an injection molding device (not shown) disposed outside the first mold 62 and fills the cavity 66 with a molten thermoplastic resin. The ejection pin 74 moves in the X (+) direction in the figure in conjunction with a mold opening operation described later, and ejects the molded product 50 (releases it). The guide pin 75 is formed in a cylindrical shape, and is fixed to the parting surface P of the first mold 62 so as to stand upright in the X direction in the drawing. The first mold 62 is provided with a temperature control device such as a heater (not shown), and the first mold 62 is adjusted to a predetermined temperature.

  The second mold 64 is provided with a hole 75a through which the guide pin 75 provided in the first mold 62 passes, and the guide pin 75 of the first mold 62 engages with the hole 75a to thereby change the first mold 62. The first mold 62 and the second mold 64 are positioned. Similarly to the first mold 62, the second mold 64 is provided with a temperature control device such as a heater (not shown), and adjusts the second mold 64 so as to have a predetermined temperature.

  The mold 60 having the above-described structure is attached to an injection molding apparatus (not shown) during the molding operation. The first mold 62 is a so-called fixed mold, and is attached to the injection nozzle side of the injection molding apparatus via a mounting plate (not shown). The second mold 64 is a so-called movable mold, and is attached to the mold moving mechanism of the injection molding apparatus via a mounting plate (not shown). Therefore, the second mold 64 can reciprocate in the X direction in FIG. 2 as the mold moving mechanism of the injection molding apparatus reciprocates in the X direction in FIG. That is, when the mold moving mechanism moves in the X (−) direction, the first mold 62 and the second mold 64 are joined with a predetermined pressure, and the mold moving mechanism moves in the X (+) direction. Thus, the first mold 62 and the second mold 64 are separated (opened). Hereinafter, the X (+) direction is referred to as a mold opening direction, and the X (−) direction is referred to as a mold clamping direction.

(For the synthetic resin molding method)
Next, a synthetic resin molding method performed using the above-described mold will be described with reference to FIG. FIG. 3 is a flowchart showing the flow of the synthetic resin molding method. As shown in FIG. 3, the synthetic resin molding method includes a mold clamping step S11, an injection step S12, a pressure holding step S13, a mold opening step S14, and a product taking out step S15.

  In the mold clamping step S11 shown in FIG. 3, the first mold 62 and the second mold 64 are joined with a predetermined pressure by moving the above-described mold moving mechanism in the X (−) direction in FIG. It is tightened. In the subsequent injection step S12, synthetic resin heated and melted is injected into the gate 72 of the first mold 62 from the injection nozzle of the injection molding apparatus. The molten resin injected into the gate 72 is filled in the cavity 66 of the mold 60. In the pressure holding step S13, the mold clamping operation is continued so that the pressure in the cavity 66 is maintained at a predetermined pressure or higher. In this pressure holding step S13, the molten resin filled in the cavity 66 is cooled and solidified. As the molten resin solidifies, the product 50 is molded in the cavity 66 of the mold 60. Then, the process proceeds to the next step.

  In the mold opening step S14 shown in FIG. 3, when the mold moving mechanism described above moves in the X (+) direction in FIG. 2, the second mold 64 also moves in the X (+) direction. An opening operation (the first mold 62 and the second mold 64 are separated) is performed. In the subsequent product removal step S15, the ejection pin 74 provided on the first mold 62 shown in FIG. 2 moves in the X (+) direction in the drawing to eject (release) the molded product 50. At this time, the synthetic resin filled and solidified in the gate 72 is easily torn off because the outer side of the gate 72 is connected to the injection nozzle of the injection molding apparatus, and the synthetic resin filled in the injection nozzle is still in a molten state. This is released together with the product 50. In this way, the product 50 is taken out from the mold 60. Thus, one cycle for forming the product 50 is completed.

  In the above description, the structure of the product 50 is simplified for convenience of description. Actually, the product 50 is rare in such a simple shape, is formed into shapes having various functions, and has many uneven shapes. Along with this, the mold 60 is also formed in a complicated uneven shape, or is formed in a double or triple structure for several slide mechanisms or two-color molding, for example. There may be.

  In the synthetic resin molding operation, the molten resin is injected from the injection nozzle at a predetermined injection pressure, and filled into the cavity 66 of the mold 60 through the gate 72 at a predetermined pressure. Therefore, the solidified synthetic resin may be in close contact with the first mold surface 68 of the first mold 62 of the mold 60 and the second mold surface 70 of the second mold 64. For example, if the solidified synthetic resin is excessively adhered to the second mold surface 70 of the second mold 64 of the mold 60, the product 50 is not reliably left in the first mold 62 in the mold opening step S14, and the product 50 A part of the second mold 64 is pulled in the X (+) direction together with the second mold 64 and deformed, or the second mold surface 70 of the second mold 64 is removed from the side surface of the product 50. Will be attached.

  Further, for example, if the solidified synthetic resin is excessively adhered to the first mold surface 68 of the first mold 62 of the mold 60, the product 50 cannot be reliably ejected by the ejection pin 74 in the product removal step S15. . That is, the product 50 may not be reliably released from the first mold surface 68 of the first mold 62. In this case, the product 50 that is not sufficiently solidified is whitened or deformed by the protrusion of the protrusion pin 74.

  In order to prevent such a problem, in the conventional method, a mold release agent such as silicone or fluorine that improves the mold release of the synthetic resin product is applied to the mold surface of the mold 60 using a nozzle. However, in this method, the mold release agent is not uniformly applied to the mold surface and the mold release does not go smoothly, or the mold release agent on the mold surface easily peels off, and the mold release agent is applied at a predetermined interval. There was a problem that productivity had to be lowered.

(Surface treatment method)
The inventors of the present invention have made researches on prevention of adhesion of a synthetic resin and improvement of releasability of a synthetic resin product from a mold. As a result, it is possible to improve the releasability of the synthetic resin product from the mold by forming a film having a liquid repellency and a low friction coefficient on the mold surface of the mold for the synthetic resin (mold) heading was. Furthermore, after conducting extensive research on a film having liquid repellency and a low coefficient of friction, when a film is formed on the mold surface by the surface treatment method described below, the releasability of the synthetic resin product from the mold There was found to be extremely improved. The present invention has been completed based on this finding.

  Hereinafter, examples of the surface treatment method will be described with reference to the drawings. FIG. 4 is a flowchart showing the flow of the surface treatment method of this embodiment, and FIG. 5 is a longitudinal sectional view for explaining the surface treatment method of this embodiment. FIG. 6 is a schematic view showing a film forming apparatus for carrying out the surface treatment method of this embodiment, and FIG. 7 shows the structure of a film formed by the surface treatment method of this embodiment and a general film. (A) shows the structure of a general film | membrane, (b) is a schematic diagram which shows the structure of the film | membrane of a present Example.

  In the surface treatment method of this example, as the first step, [1] polyorganosiloxane film forming step S21, as the second step, [2] hydroxyl group introduction treatment step S22, and as the third step, [ 3] Coupling agent treatment step S23. Hereinafter, each process will be described sequentially. In the following description, the upper side in FIGS. 5 to 7 is referred to as “upper” and the lower side is referred to as “lower”.

([1] Polyorganosiloxane film forming step S21)
First, the polyorganosiloxane film forming step S21 is performed on the first mold surface 68 of the first mold 62 and the second mold surface 70 of the second mold 64 shown in FIG. In the following description, the first mold 62 and the second mold 64 that are subjected to the surface treatment of the present embodiment are referred to as the base material 4 (see FIG. 5A).

  As shown in FIG. 5B, a polyorganosiloxane film 421 containing polyorganosiloxane is formed (film formation) on the upper surface of the substrate 4. As a method for forming the polyorganosiloxane film 421, a plasma polymerization method can be suitably used. According to the plasma polymerization method, the polyorganosiloxane film 421 having a uniform and uniform film thickness can be easily formed.

  Here, as a polyorganosiloxane, what has an organic group which forms a coupling | bonding with Si whose alkali resistance is higher than a Si-OH (Si-O) coupling | bonding is preferable. Specific examples of such polyorganosiloxanes include dialkyl silicones such as dimethyl silicone and diethyl silicone, cycloalkyl silicones, phenyl silicones, and the like, and one or more of these are combined. Can be used.

  Among these, as polyorganosiloxane, what has a dialkyl silicone (especially dimethyl silicone) as a main component is preferable. By constituting the polyorganosiloxane film 421 with dimethyl silicone as the main component, the bond between the organic group (alkyl group) and Si can be cut relatively easily in the next step [2] hydroxyl group introduction treatment step S22. A hydroxyl group can be reliably introduced into this cut portion.

  In addition, when forming the polyorganosiloxane film | membrane 421 which has dimethyl silicone as a main component using a plasma polymerization method, as the raw material (precursor), methylpolysiloxane, octamethyltrisiloxane, decamethyltetrasiloxane is mentioned, for example. , Decamethylcyclopentanesiloxane, octamethylcyclotetrasiloxane, methylphenylpolysiloxane and the like can be used alone or in combination. Such a polyorganosiloxane film 421 can be formed by, for example, a plasma polymerization method using the film forming apparatus 10 shown in FIG.

Hereinafter, a case where the polyorganosiloxane film 421 mainly composed of dimethyl silicone is formed by a plasma polymerization method will be described as an example.
A film forming apparatus 10 shown in FIG. 6 includes a vacuum chamber 12 to which a vacuum pump 11 is connected, and an electrode 13 and a stage 14 are provided in the vacuum chamber 12. The electrode 13 is attached to the upper portion of the vacuum chamber 12 via an insulator 121 and is connected to a high frequency power supply 15 disposed outside the vacuum chamber 12. This high frequency power supply 15 outputs high frequency power. The output of this high frequency power is preferably about 100 to 1000 W.

  The stage 14 is for placing the base material 4 (the first mold 62 and the second mold 64), and is disposed below the vacuum chamber 12 so as to face the electrode 13. The stage 14 is provided with a temperature adjusting mechanism (not shown) that adjusts the temperature of the substrate 4. Further, a gas supply pipe 16 and a raw material supply pipe 17 are connected to the vacuum chamber 12.

  A gas supply source 18 is connected to the gas supply pipe 16 via a flow rate control valve 161. By opening / closing the flow control valve 161, the flow rate of the gas supplied to the vacuum chamber 12 is adjusted. Examples of the additive gas supplied from the gas supply source 18 include argon, helium, nitrogen, and the like. Among these, argon is preferably used.

  A raw material container 19 for storing the above-described raw material 30 is connected to the raw material supply pipe 17 via a flow rate control valve 171. A heater 20 is installed under the raw material container 19 so that the raw material 30 in the raw material container 19 can be vaporized. The vaporized raw material 30 is sucked by the negative pressure in the vacuum chamber 12 and supplied to the vacuum chamber 12 through the raw material supply pipe 17. The flow rate of the vaporized raw material 30 supplied to the vacuum chamber 12 is controlled by the opening / closing operation of the flow rate control valve 171.

The polyorganosiloxane film 421 mainly composed of dimethyl silicone is formed by the film forming apparatus 10 as follows.
First, the substrate 4 is placed on the stage 14 in the vacuum chamber 12. Next, the raw material 30 is stored in the raw material container 19. Then, the pressure in the vacuum chamber 12 is reduced to a set value by operating the vacuum pump 11. The pressure in the vacuum chamber 12 due to this reduced pressure is preferably about 1 × 10 ^{−4 to 1} Torr.

  Next, by adjusting the temperature adjustment mechanism of the stage 14, the temperature of the substrate 4 is set so that the plasma polymerization reaction of the raw material 30 is promoted. The temperature of the substrate 4 is preferably 25 ° C. or higher, and more preferably about 25 to 100 ° C. Next, argon gas is supplied from the gas supply pipe 16 and the vaporized raw material 30 is supplied from the raw material supply pipe 17 into the vacuum chamber 12. The flow rate of argon gas is preferably about 10 to 500 sccm. On the other hand, the flow rate of the raw material 30 is preferably about 1 to 100 sccm.

Next, high frequency power is applied to the electrode 13 by the high frequency power supply 15. Thereby, argon plasma is generated in the vacuum chamber 12. Then, the weakly bonded CH ₃ group in the raw material 30 is cut by the argon plasma, and a polymerization reaction occurs in the vicinity of the surface of the substrate 4. And the product produced by this polymerization reaction couple | bonds with the surface of the base material 4, and the polyorganosiloxane film | membrane 421 (plasma polymerization film | membrane) is formed. The time for applying the high-frequency power (the formation time of the polyorganosiloxane film) is preferably about 1 to 10 minutes, and more preferably about 4 to 7 minutes.

  Note that after the polyorganosiloxane film 421 is formed in this manner, the polyorganosiloxane film 421 may be subjected to heat treatment (annealing treatment). As a result, the cross-linking reaction between the polyorganosiloxane film 421 and the surface of the substrate 4 is promoted, the hardness of the polyorganosiloxane film 421 is increased, and the adhesion between the substrate 4 and the polyorganosiloxane film 421 is strong. Become. This heat treatment is preferably performed in an inert gas atmosphere such as a nitrogen atmosphere at about 100 to 450 ° C. for about 1 to 10 minutes, more preferably about 150 to 230 ° C. for about 1 to 3 minutes.

([2] Hydroxyl introduction treatment step S22)
Next, hydroxyl group introduction treatment is performed on the obtained polyorganosiloxane film 421. As a result, some of the bonds of the CH ₃ group exposed to Si exposed on the surface of the polyorganosiloxane film 421 are cut, and a hydroxyl group is introduced into this cut portion. Thus, the film forming method of the present invention is characterized in that all of the CH ₃ groups exposed on the surface of the polyorganosiloxane film 421 are appropriately left without being replaced with hydroxyl groups.

  Next step [3] In the coupling agent treatment step S23, the coupling agent used to impart liquid repellency reacts with the hydroxyl group introduced into the surface of the polyorganosiloxane film 421 by the reactive functional group of the coupling agent. Thereby, it bonds to the surface of the polyorganosiloxane film 421. Therefore, as the amount of hydroxyl group introduced into the surface of the polyorganosiloxane film 421 is increased, the coupling amount (coupling rate) of the coupling agent is increased, and the characteristics (hereinafter referred to as the coupling agent) of the obtained film 42 are reduced. , Simply referred to as “characteristic by coupling agent”).

However, in general, a coupling agent having a functional group having a relatively large molecular weight tends to improve the characteristics due to the coupling agent. When the polyorganosiloxane film 421 is treated with such a coupling agent, Steric hindrance occurs between the functional groups, and some of the hydroxyl groups present on the surface cannot contribute to the reaction with the coupling agent. For this reason, if almost all of the CH ₃ groups exposed on the surface of the polyorganosiloxane film 421 are replaced with hydroxyl groups, as shown in FIG. 7A, a large number of hydroxyl groups that cannot be bonded to the coupling agent are present. A film remaining between the coupling agents is obtained.

  Since the portion where the hydroxyl groups remain is low in resistance to alkalis and the like, when such a film is in contact with a liquid exhibiting alkalinity for a long time, erosion starts from the portion where the hydroxyl groups remain due to the liquid, and the polyorgano The siloxane film 421 deteriorates (decomposes). As a result, the coupling agent detaches from the surface of the substrate 4 (peeling), and properties such as liquid repellency due to the coupling agent are impaired (disappeared).

On the other hand, in the present invention, the CH ₃ groups exposed on the surface of the polyorganosiloxane film 421 remain moderately. In other words, hydroxyl groups are introduced into the surface of the polyorganosiloxane film 421 sparsely (in a sparse state). For this reason, even if such a polyorganosiloxane film 421 is treated with a coupling agent having a functional group having a relatively large molecular weight, steric hindrance between the functional groups does not occur, and FIG. As shown, the coupling agent is bonded to the hydroxyl group of the polyorganosiloxane film 421.

At this time, almost all of the hydroxyl groups present on the surface of the polyorganosiloxane film 421 are consumed for bonding with the coupling agent, and on the surface of the polyorganosiloxane film 421 where the coupling agent is not bonded, CH ₃ group is exposed. In the portion where the CH ₃ group exists, high alkali resistance is exhibited. Therefore, the film 42 of the present invention exhibits both characteristics such as liquid repellency due to the coupling agent and high alkali resistance due to the polyorganosiloxane. It comes to have.

  Therefore, for example, even when such a film 42 is in contact with a liquid exhibiting alkalinity for a long period of time, erosion due to alkali is prevented or suppressed, and as a result, characteristics such as liquid repellency due to the coupling agent are prolonged. Will be maintained throughout. As a result of research and examination, the present inventors have found that the amount of hydroxyl group to be introduced can be made desired by selecting a method for hydroxyl group introduction treatment and setting the treatment conditions (particularly, treatment time). It was.

Hereinafter, the hydroxyl group introduction treatment will be described in detail.
Examples of the hydroxyl group introduction treatment include ultraviolet irradiation, plasma irradiation, electron beam irradiation, heating, and the like, and one or more of these can be used in combination. Among these, it is preferable to use plasma irradiation. According to such a method, since the substitution from the CH ₃ group to the hydroxyl group proceeds relatively moderately, the introduction amount of the hydroxyl group can be easily adjusted.

Hereinafter, the case where plasma irradiation is used as the hydroxyl group introduction treatment will be described. Examples of gas species for generating plasma include oxygen gas, nitrogen gas, inert gas (argon gas, helium gas, etc.), and one or more of these can be used in combination. . The output of the high frequency power is preferably about 50 to 500 W. By setting the output of the high frequency power within such a range, the CH ₃ group present on the surface of the polyorganosiloxane film 421 can be surely replaced with a hydroxyl group. The gas flow rate is preferably about 10 to 500 sccm, and more preferably about 100 to 300 sccm.

Note that the atmosphere in which plasma irradiation is performed may be in the air or in a reduced pressure state, but is preferably in the air. As a result, oxygen atoms are efficiently introduced from oxygen molecules and water molecules present in the atmosphere almost simultaneously with the cleavage of the organic group and Si, and therefore, CH ₃ present on the surface of the polyorganosiloxane film 421. Groups can be quickly replaced with hydroxyl groups.

In particular, for plasma irradiation, it is preferable to use oxygen plasma irradiation using a gas containing oxygen gas as a gas species for generating plasma. According to the oxygen plasma irradiation, the oxygen plasma cuts the organic group and Si and is used for bonding with Si. Therefore, the CH ₃ group present on the surface of the polyorganosiloxane film 421 is more reliably replaced with a hydroxyl group. can do.

Further, the plasma irradiation time is preferably about 1 to 10 minutes, and more preferably about 5 to 10 minutes. As a result, the CH ₃ groups present on the surface of the polyorganosiloxane film 421 are replaced with hydroxyl groups at an appropriate ratio. As a result, the finally obtained film 42 has liquid repellency due to the coupling agent. The characteristics such as the above and the alkali resistance are exhibited.

([3] Coupling agent treatment step S23)
Next, a treatment with a coupling agent is performed on the polyorganosiloxane film 421 in which part of the CH ₃ group is substituted with a hydroxyl group in the hydroxyl group introduction treatment step S22. As a result, as shown in FIG. 5C, the coupling agent is bonded to the surface of the polyorganosiloxane film 421, and a monomolecular film 422 composed of this coupling agent is formed, whereby the film 42 is obtained. It is.

  Here, there are various types of coupling agents used in this treatment. By selecting the type of functional group possessed by the coupling agent, the characteristic of the functional group (coupling) Various characteristics according to the characteristics of the agent can be imparted. For example, liquid repellency can be imparted to the film 42 by selecting a coupling agent having a liquid repellent functional group. Examples of such a functional group include a fluoroalkyl group and an alkyl group.

  Furthermore, the reactivity can be imparted to the membrane 42 by selecting a coupling agent having a reactive functional group. Examples of such a functional group include a carboxyl group, a hydroxyl group, an epoxy group, an amino group, an alkyl group, a sulfonic acid group, a carbonyl group, an aldehyde group, a nitro group, etc. An introduced alkyl group).

  Further, by using any two or more of the coupling agents having such characteristics, two or more characteristics can be imparted to the film 42. The functional group possessed by this coupling agent preferably has about 10 to 1000 carbon atoms, and more preferably about 100 to 200 carbon atoms. By setting the carbon number of this functional group within the above range, the functional groups of adjacent silane coupling agents are entangled in a complicated (three-dimensional) manner, and the liquid repellency due to the coupling agent of the film 42 is reduced. The characteristics are further improved.

  As the coupling agent, for example, various metal alkoxides having Ti, Li, Si, Na, K, Mg, Ca, St, Ba, Al, In, Ge, Bi, Fe, Cu, Y, Zr, Ta, etc. Among these, metal alkoxides having Si, Ti, Al, Zr, etc. are generally used, but it is particularly preferable to use a silane coupling agent (metal alkoxide) having Si. . As a result, the hydroxyl group of the polyorganosiloxane film 421 and the reactive functional group of the silane coupling agent are bonded relatively easily, and the monomolecular film 422 is formed on the surface of the polyorganosiloxane film 421.

  The treatment with these coupling agents includes, for example, I: an immersion method in which the polyorganosiloxane film 421 is immersed in a solution containing the coupling agent, and II: a solution containing the coupling agent is applied to the surface of the polyorganosiloxane film 421. III: A spraying method in which a solution containing a coupling agent is sprayed (showered) on the surface of the polyorganosiloxane film 421. Of these, the immersion method is preferably used. According to the dipping method, the monomolecular film 422 can be reliably formed on the surface of the polyorganosiloxane film 421 with a uniform film thickness.

Hereinafter, a case where the monomolecular film 422 is formed by an immersion method will be described.
First, a treatment solution is prepared by dissolving a coupling agent in an organic solvent. Various solvents are used as the solvent for dissolving the coupling agent, and for example, aromatic hydrocarbon solvents such as toluene, xylene, trimethylbenzene, tetramethylbenzene, and cyclohexylbenzene can be used. The concentration of the coupling agent in this treatment solution is preferably about 0.01 to 1.5 wt%.

  Next, after immersing the base material 4 on which the polyorganosiloxane film 421 is formed in this treatment solution for a predetermined time, the base material 4 is pulled up. When this base material 4 is immersed in the treatment solution of the coupling agent, the reactive functional group of the coupling agent and the hydroxyl group on the surface of the polyorganosiloxane film 421 are bonded, and the coupling agent is the polyorganosiloxane film 421. To join. Thereby, the monomolecular film 422 is formed, and the film 42 is obtained (see FIG. 5C).

  The temperature at which the substrate 4 is immersed in the treatment solution is preferably about 10 to 200 ° C, and more preferably about 20 to 100 ° C. The immersion time of the substrate 4 is preferably about 0.1 to 180 seconds, and more preferably about 10 to 60 seconds. The pulling speed of the substrate 4 is preferably about 0.5 to 50 mm / sec, and more preferably about 10 to 30 mm / sec. By setting the conditions for immersing the substrate 4 on which the polyorganosiloxane film 421 is formed in the treatment solution within the range as described above, the coupling agent is surely bonded to the polyorganosiloxane film 421. be able to.

In the film 42 formed as described above, most of the CH ₃ groups exposed on the surface of the polyorganosiloxane film 421 in the hydroxyl group introduction treatment step S22 shown in FIG. A monomolecular film 422 is formed by coupling with a coupling agent. Of these CH ₃ groups, those not substituted with hydroxyl groups will be present in the film 42 as CH ₃ groups.

  By adopting the film 42 having such a configuration, the monomolecular film 422 has a complicated (three-dimensional) entangled functional group, and thus the film 42 has excellent characteristics due to the coupling agent. . In this embodiment, the case where a film is formed on the mold surface of the synthetic resin molding die has been described as an example. However, by appropriately selecting a part for forming the film, coupling to the part on which the film is formed is performed. The characteristic by an agent can be provided.

  The surface treatment method of the present invention and the film formed thereby have been described above, but the present invention is not limited to these. For example, it goes without saying that the coupling agent used is not limited to those described above. Moreover, the surface treatment method of this invention can also add the process of 1 or 2 or more arbitrary objectives to the process as mentioned above as needed.

(Evaluation of film formed by surface treatment method)
Hereinafter, evaluation of the film formed by the surface treatment method of this example will be described. The inventors have made contact angle measurement tests and friction coefficients shown below for a metal plate having a film 42 formed by the above-described surface treatment method and a metal plate having a film formed by another known surface treatment method, respectively. the measurement test was carried out.

  First, the contact angle measurement test will be described. In the contact angle measurement test, the metal plate M1 subjected to the surface treatment method of this example, the metal plate M2 provided with a TiAlN (titanium nitride aluminum) coating excellent in wear resistance and sliding properties, and the smoothness of the film. A metal plate M3 having a DLC (Diamond Like Carbon) coating, which is an amorphous film having a high and low friction coefficient, is prepared. And hexadecane is dripped at these metal plates M1-3 as a pure water and a highly viscous liquid, and a contact angle with the metal plates M1-3 is measured.

  As a result, the contact angles of pure water and hexadecane were as follows: metal plate M1> metal plate M2> metal plate M3. That is, the film formed by the surface treatment method of this example showed higher liquid repellency than the TiAlN coating film and the DLC coating film. In particular, the film formed by the surface treatment method of this example had a contact angle of 100 degrees or more with respect to pure water and a contact angle of 60 degrees or more with respect to hexadecane.

  Next, the friction coefficient measurement test will be described. In the friction coefficient measurement test, a commercially available friction and wear tester is used, and a ball formed of PP (polypropylene) is pressed against the above-described metal plates M1 to M3 with a load of 500 g, and a distance of 10 mm is applied to each film. Was slid 5 times and the coefficient of friction was measured. As a result, the friction coefficient was as follows: metal plate M1 <metal plate M2 <metal plate M3. That is, the film formed by the surface treatment method of this example showed a lower coefficient of friction than the TiAlN coating film and the DLC coating film. In particular, the film formed by the surface treatment method of this example has a friction coefficient of 0.1 or less, which is much lower than the friction coefficient 0.3 of the TiAlN coating film and the friction coefficient 0.4 of the DLC coating film. It was.

Following, the effect of this embodiment.
(1) In the surface treatment method of the above-mentioned synthetic resin molding die, a polyorganosiloxane film is formed on the mold surface by a plasma polymerization method, and a hydroxyl group is introduced into the polyorganosiloxane film by plasma irradiation. . Then, the polyorganosiloxane film introduced with a hydroxyl group is treated with a coupling agent. By doing in this way, the film | membrane which exhibits the characteristic according to the kind of coupling agent can be formed in the type | mold surface of a synthetic resin shaping | molding die. By employing a coupling agent having releasability as a characteristic, a synthetic resin molding die having a film having excellent releasability on the mold surface can be provided.

  (2) As the coupling agent, by adopting at least one of those having a liquid repellent functional group or those having a reactive functional group, the mold surface of the synthetic resin molding die has liquid repellency. A film having the same can be formed. A film having liquid repellency is excellent in releasability for releasing a synthetic resin product from a synthetic resin mold. Therefore, a synthetic resin molding die having a film excellent in releasability can be provided.

  (3) By applying the plasma polymerization method to the surface treatment method for the synthetic resin molding die described above, a polyorganosiloxane film (base film) having a uniform and uniform film thickness can be formed. Therefore, the film having releasability also has a uniform and uniform film thickness. Therefore, the manufactured synthetic resin product surely reflects the shape of the synthetic resin molding die. In particular, it is effective for molding a synthetic resin having a complicated shape.

  (4) A film to which the above-described surface treatment method for a synthetic resin molding die is applied has excellent liquid repellency and can reduce frictional resistance. Therefore, the peel strength and release resistance of the synthetic resin product from the synthetic resin molding die can be reduced. The mold release time can be shortened and the productivity of synthetic resin products is improved.

  (5) In the synthetic resin molding die surface treatment method described above, a film having liquid repellency is formed on the entire mold surface of the synthetic resin molding die. Therefore, corrosion of the mold surface of the synthetic resin molding die can be reduced.

  DESCRIPTION OF SYMBOLS 4 ... Base material, 10 ... Film-forming apparatus, 11 ... Vacuum pump, 12 ... Vacuum chamber, 14 ... Stage, 42 ... Membrane, 50 ... Product, 60 ... Mold as a synthetic resin molding die, 62 ... 1st metal Mold, 64 ... second mold, 66 ... cavity, 68 ... first mold surface, 70 ... second mold surface, 72 ... gate, 74 ... extrusion pin, 421 ... polyorganosiloxane film, 422 ... monomolecular film, S21 ... a polyorganosiloxane film forming step as the first step, S22 ... a hydroxyl group introduction treatment step as the second step, S23 ... a coupling agent treatment step as the third step.

Claims (10)

A synthetic resin molding die surface treatment method for filling a molten synthetic resin in a mold and solidifying the synthetic resin in the mold to mold a synthetic resin molded article,
A first step of forming a polyorganosiloxane film containing polyorganosiloxane on the mold surface of the synthetic resin molding die;
A second step of subjecting the polyorganosiloxane film to a hydroxyl group introduction treatment for cleaving some organic groups exposed on the surface and introducing hydroxyl groups;
A synthetic resin molding die surface treatment method comprising: a third step of coupling the polyorganosiloxane film subjected to the hydroxyl group introduction treatment with a coupling agent.   2. The surface treatment method for a synthetic resin molding die according to claim 1, wherein the polyorganosiloxane film is mainly composed of a dialkyl silicone.   3. The surface treatment method for a synthetic resin molding die according to claim 1, wherein in the first step, the polyorganosiloxane film is formed by a plasma polymerization method. 4.   The surface treatment method for a synthetic resin molding die according to any one of claims 1 to 3, wherein the hydroxyl group introduction treatment in the second step is performed by plasma irradiation.   The surface treatment method for a synthetic resin molding die according to claim 4, wherein the plasma irradiation time in the plasma irradiation is 5 to 10 minutes.   6. The surface treatment method for a synthetic resin molding die according to claim 4, wherein an output of the high frequency power in the plasma irradiation is 50 to 500 W. 7.   The surface treatment method for a synthetic resin molding die according to any one of claims 1 to 6, wherein the coupling agent is a silane coupling agent.   The surface treatment method for a synthetic resin molding die according to any one of claims 1 to 7, wherein the coupling agent has a functional group having 10 to 1000 carbon atoms.   The said coupling agent is at least 1 sort (s) of what has a liquid-repellent functional group, or has a reactive functional group, The Claim 1 thru | or 8 characterized by the above-mentioned. Surface treatment method for synthetic resin molding die.   A synthetic resin molding die having a film formed by the surface treatment method for a synthetic resin molding die according to any one of claims 1 to 9.

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