Just because Scotty gave the man a advanced chemical formula, doesn't mean the man would have been able to create transparent aluminum using mid-eighties technology.
Maybe not, but the simple action causes hell with the timeline. It branches off from one brach to thousands in the consequences. Off the top of my head (but it's way too complex and deep to address):
-- Even if his company couldn't make it, he filed patents.
-- New programs and machinery are made to handle trying to make it.
-- The very act of trying to get it done may require hiring additional personnel, temporary personnel, or just give existing employees more hours, which takes time away from their lives they spent doing something else and more money in their pockets which will be spent in ways that branch out again.
-- Scotty spoke to the mouse. That meant nothing then, but when technology starts changing and you can speak to computers, the boss might remember that and have new ideas and new patents and invent something he wouldn't have before.
-- Even failure produces results. Science is full of failures that lead to something else, so who knows what will happen even if he fails making transparent alluminum.
There's just so, so, so, so, so many braches. Scotty didn't just cause a butterfly to flap its wings, he blew it up. And not to forget: Chekov threw his hand phaser away! Idiot. So what if it doesn't work? Taht doesn't mean you leave it in the past!